4. EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017
Earnings Per Share [Abstract]
Numerator: Net (loss) income	$ (629)	$ 60	$ (2,144)	$ 70
Denominator for basic net (loss) income per share: Weighted average shares outstanding (in thousands)	22,294	21,645	22,242	21,531
Shares used in basic net (loss) income per share calculation (in thousands)	22,294	21,645	22,242	21,531
Effect of dilutive securities (in thousands)	0	1,238	0	1,406
Denominator for diluted net (loss) income per share (in thousands)	22,294	22,883	22,242	22,937
Basic net (loss) income per share	$ (0.03)	$ 0.00	$ (0.10)	$ 0.00
Diluted net (loss) income per share	$ (0.03)	$ 0.00	$ (0.10)	$ 0.00