10. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2018	May 31, 2017
Accumulated other comprehensive income, beginning	$ 2,249	$ 2,237
Other comprehensive income (loss) before reclassifications	43	12
Amounts reclassified out of AOCI	0	0
Other comprehensive income (loss), net of tax	43	12
Accumulated other comprehensive income, ending	2,292	2,249
Cumulative Translation Adjustments [Member]
Accumulated other comprehensive income, beginning	2,249	2,237
Other comprehensive income (loss) before reclassifications	43	12
Amounts reclassified out of AOCI	0	0
Other comprehensive income (loss), net of tax	43	12
Accumulated other comprehensive income, ending	2,292	2,249
Unrealized loss on Investments, Net
Accumulated other comprehensive income, beginning	0	0
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified out of AOCI	0	0
Other comprehensive income (loss), net of tax	0	0
Accumulated other comprehensive income, ending	$ 0	$ 0