STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2020

Stock-Based Compensation [Abstract]

Components of Stock-based Compensation Expense

The following table summarizes the components of stock-based compensation expense included in the consolidated statements of operations:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Stock-Based Compensation Expense:
Cost of revenue	$	44	$	154	$	132	$	213
Sales and marketing expense		237		172		495		252
Research and development expense		193		759		568		939
General and administrative expense		2,305		472		3,128		1,515
	$	2,779	$	1,557	$	4,323	$	2,919

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Stock-based compensation expense by type:
Employee stock purchase plan	$	2,651	$	1,329	$	3,717	$	1,841
Non-employee stock purchase plan		44		228		356		1,078
Subsidiary option grants		84		-		250		-
	$	2,779	$	1,557	$	4,323	$	2,919

Assumptions Used to Determine Fair Value of Share Options Granted

The fair value of options granted to employee and non-employee with a service period based condition is estimated on the grant date using the Black-Scholes valuation model with the following assumptions.

	Nine Months Ended September 30,	Year Ended December 31,
	2020	2019
Fair value of common share(1)	$22.07-85.27	$13.64-16.81
Expected term in years(2)	5.50-6.25	6.25
Volatility(3)	42.17%-48.15%	39.91%-40.35%
Risk-free interest rate(4)	0.27%-0.82%	1.69%-2.46%
Expected dividend(5)	0%	0%

(1) Fair value of Class A common stock value was the closing market price of the Class A common stock on the grant date.

(2) Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110.

(3) Volatility is calculated based on the historical volatility of the stock of companies comparable to ACM in the period equal to the expected term of each grant.

(4) Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.

(5) Expected dividend is assumed to be 0% as ACM has no history or expectation of paying a dividend on its common stock.

The fair value of option granted to employee with market based condition is estimated on the grant date using the Monte Carlo simulation model with the following assumptions.

	Nine Months Ended  September 30,
	2020
Fair value of common share(1)	$22.07
Expected term in years(2)	9.20 - 9.80
Volatility(3)	45.10%
Risk-free interest rate(4)	2.68%
Expected dividend(5)	0%

(1) Fair value of Class A common stock value was the closing market price of the Class A common stock on the grant date.

(2) Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110.

(3) Volatility is calculated based on the historical volatility of the stock of companies comparable to ACM in the period equal to the expected term of each grant.

(4) Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.

(5) Expected dividend is assumed to be 0% as ACM has no history or expectation of paying a dividend on its common stock.

Employee Share Option [Member]

Stock-Based Compensation [Abstract]

Summary of Share Option Activities

The following table summarizes the Company’s employee share option activities during the nine months ended September 30, 2020:

	Number of Option Share			Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2019		2,994,063		$	2.59	$	6.77	7.05 years
Granted		778,399			11.98		28.70
Exercised		(327,917	)		1.56		4.33
Expired		-			-		-
Forfeited/cancelled		(40,515	)		4.94		13.04
Outstanding at September 30, 2020		3,404,030		$	4.81	$	11.95	7.14 years
Vested and exercisable at September 30, 2020		2,061,793

Employee Share Option [Member] | ACM Shanghai [Member]

Stock-Based Compensation [Abstract]

Summary of Share Option Activities

The following table summarizes the ACM Shanghai employee stock option activities during the nine months ended September 30, 2020:

	Number of Option Shares in ACM Shanghai			Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2019		-		$	-	$	-		-
Granted		5,869,808			0.22		1.87
Exercised		-			-		-
Expired		-			-		-
Forfeited/cancelled		(330,770	)		0.23		1.87
Outstanding at September 30, 2020		5,539,038		$	0.22	$	1.87	3.76 years
Vested and exercisable at September 30, 2020		-

Non-Employee Stock Option [Member]

Stock-Based Compensation [Abstract]

Summary of Share Option Activities

The following table summarizes ACM’s non-employee stock option activities during the nine months ended September 30, 2020:

	Number of Option Shares			Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2019		1,101,613		$	0.82	$	2.69	5.85 years
Granted		20,000			10.29		25.60
Exercised		(265,029	)		0.91		3.34
Expired		-
Forfeited/cancelled		(111	)		0.30		0.75
Outstanding at September 30, 2020		856,473		$	1.01	$	3.02	5.11 years
Vested and exercisable at September 30, 2020		819,819