4. EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Earnings Per Share [Abstract]
Numerator: Net income (loss)	$ 245	$ (3,201)	$ 83	$ (5,345)
Denominator for basic net income (loss) per share: Weighted average shares outstanding (in thousands)	22,937	22,459	22,823	22,314
Shares used in basic net income (loss) per share calculation (in thousands)	22,937	22,459	22,823	22,314
Effect of dilutive securities (in thousands)	193	0	117	0
Denominator for diluted net income (loss) per share (in thousands)	23,130	22,459	22,940	22,314
Basic net income (loss) per share	$ 0.01	$ (0.14)	$ 0.00	$ (0.24)
Diluted net income (loss) per share	$ 0.01	$ (0.14)	$ 0.00	$ (0.24)