STOCK-BASED COMPENSATION, Share Option Activities (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	May 31, 2023	Mar. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Employee Share Option
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares)		9,211,641	9,211,641
Granted (in shares)			2,202,000
Exercised (in shares)			(680,319)
Forfeited/cancelled (in shares)			(44,560)
Outstanding, end of period (in shares)			10,688,762	9,211,641
Vested and exercisable (in shares)			6,356,350
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share)		$ 3.58	$ 3.58
Granted (in dollars per share)			10.34
Exercised (in dollars per share)			0.89
Forfeited/cancelled (in dollars per share)			10.65
Outstanding at end of period (in dollars per share)			5.15	$ 3.58
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share)		$ 8.24	8.24
Granted (in dollars per share)			13.87
Exercised (in dollars per share)			2.24
Forfeited/cancelled (in dollars per share)			21.76
Outstanding, end of period (in dollars per share)			$ 9.59	$ 8.24
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term			6 years 4 months 9 days	6 years 4 months 9 days
Unrecognized employee stock-based compensation expense			$ 30,703	$ 16,009
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition		4 years 14 days	3 years 10 months 24 days
Employee Share Option | ACM Shanghai
Number of Option Share [Roll Forward]
Exercised (in shares)	(2,150,309)
Weighted Average Grant Date Fair Value
Granted (in dollars per share)			$ 9.24
Weighted Average Exercise Price
Granted (in dollars per share)			$ 7.10
Employee Share Option | ACM Shanghai | 2019 Stock Option Incentive Plan
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares)		5,377,500	5,377,500
Exercised (in shares)			(2,150,309)
Forfeited/cancelled (in shares)			(92,308)
Outstanding, end of period (in shares)			3,134,883	5,377,500
Vested and exercisable (in shares)			492,308
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share)		$ 0.23	$ 0.23
Exercised (in dollars per share)			0.20
Forfeited/cancelled (in dollars per share)			0.22
Outstanding at end of period (in dollars per share)			0.23	$ 0.23
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share)		$ 1.93	1.93
Exercised (in dollars per share)			1.85
Forfeited/cancelled (in dollars per share)			1.85
Outstanding, end of period (in dollars per share)			$ 1.90	$ 1.93
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term			1 year 1 month 6 days	1 year 9 months 3 days
Employee Share Option | ACM Shanghai | 2023 Stock Option Incentive Plan
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares)		0	0
Granted (in shares)			10,648,500
Outstanding, end of period (in shares)			10,648,500	0
Vested and exercisable (in shares)			0
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share)		$ 0	$ 0
Outstanding at end of period (in dollars per share)			9.24	$ 0
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share)		$ 0	0
Outstanding, end of period (in dollars per share)			$ 7.10	$ 0
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term			3 years 4 months 2 days	0 years
Non-Employee Stock Option
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares)		1,483,658	1,483,658
Exercised (in shares)			(239,129)
Forfeited/cancelled (in shares)			(10,957)
Outstanding, end of period (in shares)			1,233,572	1,483,658
Vested and exercisable (in shares)			1,226,072
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share)		$ 0.38	$ 0.38
Exercised (in dollars per share)			0.24
Forfeited/cancelled (in dollars per share)			0.22
Outstanding at end of period (in dollars per share)			0.41	$ 0.38
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share)		$ 1.15	1.15
Exercised (in dollars per share)			0.56
Forfeited/cancelled (in dollars per share)			0.50
Outstanding, end of period (in dollars per share)			$ 1.27	$ 1.15
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term			2 years 10 months 6 days	3 years 8 months 4 days
Unrecognized employee stock-based compensation expense			$ 21	$ 55
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition			5 months 12 days	1 year 2 months 12 days
Non-Employee Stock Option | ACM Shanghai | 2019 Stock Option Incentive Plan
Weighted Average Remaining Contractual Term
Unrecognized employee stock-based compensation expense			$ 38	$ 160
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition			9 months	3 months
Non-Employee Stock Option | ACM Shanghai | 2023 Stock Option Incentive Plan
Weighted Average Remaining Contractual Term
Unrecognized employee stock-based compensation expense			$ 90,197	$ 0
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition			2 years 4 months 2 days