4. EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Earnings Per Share [Abstract]
Numerator: Net income (loss)	$ 251	$ (629)	$ (162)	$ (2,144)
Denominator for basic net income (loss) per share: Weighted average shares outstanding (in thousands)	22,823	22,294	22,765	22,242
Shares used in basic net income (loss) per share calculation (in thousands)	22,823	22,294	22,765	22,242
Effect of dilutive securities (in thousands)	89	0	0	0
Denominator for diluted net income (loss) per share (in thousands)	22,912	22,294	22,765	22,242
Basic net income (loss) per share	$ 0.01	$ (0.03)	$ (0.01)	$ (0.10)
Diluted net income (loss) per share	$ 0.01	$ (0.03)	$ (0.01)	$ (0.10)