The applicable income tax rate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2024-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_81_c_ii&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_ApplicableTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 7
-IssueDate 2024-01-01
-Paragraph 45
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2024-en-r&anchor=para_45&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2024-01-01
-Paragraph B13
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2024-en-r&anchor=para_B13_a&doctype=Appendix&subtype=B
-URIDate 2024-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 54
-Subparagraph i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_54_i&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_CashAndCashEquivalents
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The proportion of the voting rights in an associate held by the entity. [Refer: Total for all associates [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 17
-Subparagraph b
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2024-en-r&anchor=para_17_b_iii&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2024-en-r&anchor=para_16_b_iii&doctype=Standard
-URIDate 2024-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2024-01-01
-Paragraph 21
-Subparagraph a
-Clause iv
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2024-en-r&anchor=para_21_a_iv&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_ProportionOfVotingPowerHeldInAssociate
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The useful life, measured as period of time, used for intangible assets other than goodwill. [Refer: Intangible assets other than goodwill]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2024-01-01
-Paragraph 118
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=38&code=ifrs-tx-2024-en-r&anchor=para_118_a&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_UsefulLifeMeasuredAsPeriodOfTimeIntangibleAssetsOtherThanGoodwill
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash deposit insured.

+ References

No definition available.

+ Details

Name:	omse_CashDepositInsured
Namespace Prefix:	omse_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Closing foreign exchange rate calculated using reporting currency.

+ References

No definition available.

+ Details

Name:	omse_ClosingForeignExchangeRateCalculatedUsingReportingCurrency
Namespace Prefix:	omse_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Material accounting policies details.

+ References

No definition available.

+ Details

Name:	omse_MaterialAccountingPoliciesDetailsLineItems
Namespace Prefix:	omse_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of reportable segments.

+ References

No definition available.

+ Details

Name:	omse_NumberOfReportableSegments1
Namespace Prefix:	omse_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_ClassesOfIntangibleAssetsOtherThanGoodwillAxis=ifrs-full_ComputerSoftwareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CurrencyInWhichInformationIsDisplayedAxis=omse_BruneiDollarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CurrencyInWhichInformationIsDisplayedAxis=omse_IndonesianRupiahMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CurrencyInWhichInformationIsDisplayedAxis=omse_MalaysianRinggitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CurrencyInWhichInformationIsDisplayedAxis=currency_SGD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CurrencyInWhichInformationIsDisplayedAxis=omse_ThaiBahtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_SG
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_SA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_MY
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_ID
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_TH
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Material Accounting Policies - Additional Information (Details) ฿ in Millions, Rp in Billions	3 Months Ended	10 Months Ended	12 Months Ended
	Jun. 15, 2023 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2025 USD ($) Segment	Mar. 31, 2023 USD ($)	Mar. 31, 2025 BND ($)	Mar. 31, 2025 IDR (Rp)	Mar. 31, 2025 MYR (RM)	Mar. 31, 2025 SGD ($)	Mar. 31, 2025 THB (฿)
Material accounting policies details [Line Items]
Closing foreign exchange rate calculated using reporting currency			$ 1
Cash deposits in bank accounts	$ 27,666,000	$ 43,470,000	$ 72,950,000	$ 29,527,000
Applicable tax rate	17.00%	17.00%	17.00%	17.00%
Number of reportable segments \| Segment			6
Software
Material accounting policies details [Line Items]
Estimated useful life			5 years
Bottom of Range
Material accounting policies details [Line Items]
Percentage of voting power of another entity			20.00%
Top of Range
Material accounting policies details [Line Items]
Percentage of voting power of another entity			50.00%
Brunei Dollar
Material accounting policies details [Line Items]
Cash deposit insured					$ 50,000
Indonesian Rupiah
Material accounting policies details [Line Items]
Cash deposit insured \| Rp						Rp 2
Malaysian Ringgit
Material accounting policies details [Line Items]
Cash deposit insured \| RM							RM 250,000
Singapore Dollar
Material accounting policies details [Line Items]
Cash deposit insured								$ 100,000
Thai Baht
Material accounting policies details [Line Items]
Cash deposit insured \| ฿									฿ 1
Singapore
Material accounting policies details [Line Items]
Applicable tax rate			17.00%
Saudi
Material accounting policies details [Line Items]
Applicable tax rate			20.00%
Malaysia
Material accounting policies details [Line Items]
Applicable tax rate			24.00%
Indonesia
Material accounting policies details [Line Items]
Applicable tax rate			22.00%
Thailand
Material accounting policies details [Line Items]
Applicable tax rate			20.00%