2. STOCK-BASED COMPENSATION (Details Narrative) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014
Stock-based compensation costs capitalized as part of inventory	$ 0	$ 60	$ 0	$ 60
Stock-based compensation expense related to stock options	233	245	518	407
Intrinsic value of options exercised	125	29	$ 185	435
Weighted average remaining contractual life of the options exercisable and expected to be exercisable			4 years 6 months 29 days
Employee Stock Purchase Plan
Stock-based compensation related to the ESPP	21	$ 32	$ 55	$ 67
Compensation cost related to purchase rights under the ESPP but not yet recognized	75		$ 75
Weighted average period for recognition of costs			1 year
1996 Stock Option Plan and 2006 Equity Incentive Plan
Unrecognized stock-based compensation	1,508		$ 1,508
Estimated forfeitures of unvested stock based awards, amount	$ 4		$ 4
Weighted average period for recognition of costs			2 years 3 months 18 days
Restricted Stock Units
Restricted Stock Units granted			35,000
Market value on the date of the grant			$ 2.16