ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 13,777	$ 24,185	$ 22,207
Credit card receivables	1,900	1,200
Cash and cash equivalents held in bank accounts in foreign countries	11,300	22,600
Restricted Cash, Current	944	944	944
Restricted Cash, Noncurrent	476	503	4,346
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	15,197	$ 25,632	$ 27,497
GSX KOREA
Cash and Cash Equivalents [Line Items]
Net assets	$ 21,300