2. STOCK-BASED COMPENSATION (Details Narrative) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended
	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Stock-based compensation costs capitalized as part of inventory	$ 0			$ 0	$ 0	$ 0
Intrinsic value of options exercised	154			0	$ 564	185
Weighted average remaining contractual life of the options exercisable and expected to be exercisable					3 years 10 months 6 days
2006 and 2016 Equity Incentive Plans
Unrecognized stock-based compensation	1,081				$ 1,081
Estimated forfeitures of unvested stock based awards, amount	3				$ 3
Weighted average period for recognition of costs					2 years 4 months 24 days
Employee Stock Purchase Plan
Stock-based compensation related to the ESPP	25			$ 23	$ 96	$ 78
Compensation cost related to purchase rights under the ESPP but not yet recognized	$ 52				$ 52
Weighted average period for recognition of costs					9 months 18 days
ESPP shares issued	0			0	65	36
ESPP purchase right granted	0			0	0	0
ESPP shares available for issuance	467				467
RSU Transactions
Restricted Stock Units granted (in thousands)	19				157
Market value on the date of the grant	$ 2.46				$ 1.78
Stock Option and RSU Transactions
Shares reserved under 2016 Equity Incentive plan (in thousands)		2,238
Stock-based compensation expense related to stock options and RSUs	$ 232			$ 190	$ 695	$ 708
Restricted Stock Units granted (in thousands)	19		138