5. INCOME TAXES - Statutory income tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
INCOME TAXES
U.S. Federal taxes at statutory rate	$ (1,282)	$ (17)	$ (956)
State taxes, net of federal benefit		3	(204)
Deemed repatriation transfer tax	5,117
Deferred tax re-measurement, change in tax rates	1,093
Stock-based compensation	(124)	630	470
Tax credits	(417)	(398)	(539)
Foreign tax rate differential	390	(1,525)	(368)
Tax exempt interest	(8)	(5)	(9)
Non-deductible expenses and other	97	24	6
Income tax expense (benefit) before change in valuation allowance	4,866	(1,288)	(1,600)
Valuation allowance	(4,413)	1,354	959
Provision (benefit) for income taxes	$ 453	$ 66	$ (641)