SC 13D/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 6)*

RAE Systems Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

75061P 10 2

(CUSIP Number)

Robert I. Chen	Robert T. Ishii
c/o RAE Systems, Inc.	Wilson Sonsini Goodrich & Rosati,
3775 North First Street	Professional Corporation
San Jose, California 95134	One Market Street, Spear Tower Suite 3300
	San Francisco, California 94105
(408) 952-8200	(650) 947-2000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

May 25, 2011

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

Note:  Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

1	NAMES OF REPORTING PERSONS:             Robert I. Chen
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             United States of America

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                  0
	8    SHARED VOTING POWER:                  15,834,942
	9    SOLE DISPOSITIVE POWER:                  270,833
	10    SHARED DISPOSITIVE POWER:                  15,564,109

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:              15,834,942*
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):              26.6%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

* Includes options to purchase 270,833 shares of common stock of issuer exercisable within 60 days.

2

1	NAMES OF REPORTING PERSONS:             Lien Q. Chen
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             United States of America

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                 0
	8    SHARED VOTING POWER:                 15,564,109
	9    SOLE DISPOSITIVE POWER:                 0
	10    SHARED DISPOSITIVE POWER:                 15,564,109

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:             15,564,109
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):              26.2%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

3

1	NAMES OF REPORTING PERSONS:             Chen Revocable Trust DTD 5/8/2001
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             California

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                 0
	8    SHARED VOTING POWER:                  15,382,849
	9    SOLE DISPOSITIVE POWER:                 0
	10    SHARED DISPOSITIVE POWER:                  15,382,849

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):              25.8%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

4

1	NAMES OF REPORTING PERSONS:             Chen Family Foundation
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             California

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                  0
	8    SHARED VOTING POWER:                  181,260
	9    SOLE DISPOSITIVE POWER:                 0
	10    SHARED DISPOSITIVE POWER:                 181,260

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:             181,260
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):              0.3%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

5

1	NAMES OF REPORTING PERSONS:             Peter Hsi
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             United States of America

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                 0
	8    SHARED VOTING POWER:                 2,757,998
	9    SOLE DISPOSITIVE POWER:                 66,666
	10    SHARED DISPOSITIVE POWER:                 2,691,332

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:             2,757,998*
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):             4.6%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

* Includes options to purchase 66,666 shares of common stock of issuer exercisable within 60 days.

6

1	NAMES OF REPORTING PERSONS:             Sandy Hsi
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             United States of America

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                  0
	8    SHARED VOTING POWER:                 2,691,332
	9    SOLE DISPOSITIVE POWER:                 0
	10    SHARED DISPOSITIVE POWER:                 2,691,332

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:             2,691,332
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):             4.5%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

7

1	NAMES OF REPORTING PERSONS:             Hsi Family Trust
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a)  ¨ (b)  x
3	SEC USE ONLY:
4	SOURCE OF FUNDS (SEE INSTRUCTIONS):             OO
5	CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e):              ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION:             California

NUMBER OF   SHARES   BENEFICIALLY   OWNED BY   EACH   REPORTING   PERSON   WITH	7    SOLE VOTING POWER:                  0
	8    SHARED VOTING POWER:                 2,691,332
	9    SOLE DISPOSITIVE POWER:                 0
	10    SHARED DISPOSITIVE POWER:                 2,691,332

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:             2,691,332
12	CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):              x             (See Item 6)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):              4.5%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):             OO

8

This Amendment No. 6 (this “Amendment No. 6”) to the statement on Schedule 13D, filed with the Securities and Exchange Commission on behalf of the Reporting Persons relating to the Common Stock of RAE Systems, Inc., a Delaware corporation (“RAE”), on September 29, 2010, as amended and restated (the “Schedule 13D”) is being filed pursuant to Rule 13d-2 of the Securities Exchange Act, as amended, on behalf of the Reporting Persons to amend certain information set forth below to the items indicated. Unless otherwise stated herein, all capitalized terms used in this Amendment No. 6 shall have the same meaning as those set forth in the Schedule 13D.

Item 4. Purpose of Transaction.

Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following:

On May 25, 2011, Purchaser, Merger Sub and RAE entered into Amendment No. 4 to the Merger Agreement (“Amendment No. 4 to the Merger Agreement”), pursuant to which, among other things, the Merger Consideration was increased to $2.25 per share, payable in cash, without interest. Purchaser and Merger Sub are each affiliates of Vector Capital IV, L.P., Vector Entrepreneur Fund III, L.P. and Vector Capital III, L.P. (together, “Vector”)

Concurrently with the execution of Amendment No. 4 to the Merger Agreement, the Chen Revocable Trust DTD 5/8/2001 (the “RLC Trust”) entered into an Amendment No. 2 to its Rollover Agreement (“Amendment No. 2 to the RLC Rollover Agreement”) which provides that the number of shares to be contributed by the RLC Trust for no consideration would increase to approximately 1.98 million shares, which have a value of approximately $4.45 million at $2.25 per share, which increase resulted from both the deal price increase and the price point beyond which upside is sacrificed moving from $1.75 per share down to $1.30 per share.

References to, and descriptions of Amendment No. 2 to the RLC Rollover Agreement throughout this statement are qualified in their entirety by reference to Amendment No. 2 to the RLC Rollover Agreement included as Exhibit 6 hereto and which is incorporated herein by reference.

9

Item 7. Materials to be Filed as Exhibits.

Item 7 of the Schedule 13D is hereby amended to add the following exhibit:

  6 Amendment No. 2, dated as of May 25, 2011, to Rollover Agreement, dated as of January 18, 2011, as amended, by and between RAE and RLC Trust

10

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: May 25, 2011
CHEN REVOCABLE TRUST DTD 5/8/2001		CHEN FAMILY FOUNDATION
By:	/S/    ROBERT I. CHEN	By:	/S/    ROBERT I. CHEN
	Robert I. Chen		Robert I. Chen
	Trustee
By:	/S/    LIEN Q. CHEN	By:	/S/    LIEN Q. CHEN
	Lien Q. Chen		Lien Q. Chen
	Trustee
ROBERT I. CHEN		LIEN Q. CHEN
By:	/S/    ROBERT I. CHEN	By:	/S/    LIEN Q. CHEN
HSI FAMILY TRUST		PETER HSI
By:	/S/    PETER HSI	By:	/S/    PETER HSI
	Peter Hsi
	Trustee
		SANDY HSI
By:	/S/    SANDY HSI	By:	/S/    SANDY HSI
	Sandy Hsi
	Trustee

11

EXHIBIT INDEX

Exhibit No.	Title
6	Amendment No. 2, dated as of May 25, 2011, to Rollover Agreement, dated as of January 18, 2011, as amended, by and between RAE and RLC Trust

EX-99.6

Exhibit 6

AMENDMENT NO. 2 TO ROLLOVER AGREEMENT

This Amendment No. 2 (this “Amendment No. 2”) to that certain Rollover Agreement, dated as of January 18, 2011, as amended (the “Rollover Agreement”), by and between RAY HOLDING CORPORATION, a Delaware corporation (the “Company”) and CHEN REVOCABLE TRUST DTD 5/8/2011 (the “Investor”), is made and entered into as of May 25, 2011 by and between the Company and the Investor. All capitalized terms that are used in this Amendment No. 2 but not defined in this Amendment No. 2 shall have the respective meanings ascribed thereto in the Rollover Agreement.

A.     On May 24, 2011, Parent, Merger Sub and the Company entered into Amendment No. 4 to the Merger Agreement (“Amendment No. 4 to the Merger Agreement”).

B.     In connection with Amendment No. 4 to the Merger Agreement, the Investor and the Company desire to enter into this Amendment No. 2, and the Investor believes it is in its best interests to enter into this Amendment No. 2 and consummate the transactions contemplated hereby, by the Rollover Agreement and by the Merger Agreement.

NOW, THEREFORE, the parties hereto hereby agree as follows:

1.     Rollover Amount.

Recital C of the Rollover Agreement is hereby amended and restated in its entirety as set forth below:

C.     In connection with the transactions contemplated by the Merger Agreement (the “Contemplated Transactions”), the Investor desires, immediately prior to the consummation of the Merger on the Closing Date, to contribute to the Company (i) that number of shares of Target Common Stock as set forth on Exhibit A attached hereto (the “Exchange Shares”) having a per share purchase price equal to the Merger Consideration (the aggregate purchase price for the shares of Target Common Stock to be exchanged by the Investor shall be referred to herein as the “Rollover Amount”) and (ii) that number of shares of Target Common Stock as set forth on Exhibit A attached hereto under the heading “Transferable Shares” (the “Transferable Shares”).

Exhibit A to the Rollover Agreement is hereby amended and restated in its entirety and replaced by Exhibit A to this Amendment No. 2.

2.     Rollover Agreement References. The parties hereto hereby agree that all references to the “Agreement” set forth in the Rollover Agreement (including, without limitation, in the representations and warranties of the parties set forth therein) shall be deemed to be references to the Rollover Agreement as amended by this Amendment No. 2.

3.     Full Force and Effect. Except as expressly amended or modified hereby, the Rollover Agreement and the agreements, documents, instruments and certificates among the

parties hereto as contemplated by, or referred to, in the Rollover Agreement shall remain in full force and effect without any amendment or other modification thereto.

4.     Counterparts. This Amendment No. 2 may be executed in several counterparts, each of which shall be deemed an original and all of which shall constitute one and the same instrument. The exchange of a fully executed Amendment No. 2 (in counterparts or otherwise) by facsimile shall be sufficient to bind the parties to the terms and conditions of this Amendment No. 2.

[Remainder of page intentionally left blank]

IN WITNESS WHEREOF, the parties have executed this Amendment No. 2 as of the date first written above.

RAY HOLDING CORPORATION
By:	/s/ David Baylor
	Name:	David Baylor
	Title:	President
CHEN REVOCABLE TRUST DTD 5/8/2001
/s/ Robert I. Chen
By: Robert I. Chen, Trustee
/s/ Lien Q. Chen
By: Lien Q. Chen, Trustee

Amendment No. 2 Signature Page