4. EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Net (loss) income per share:
Numerator: Net (loss) income	$ (735)	$ 245	$ (2,594)	$ 83
Denominator for basic net (loss) income per share: Weighted average shares outstanding (in thousands)	23,525	22,937	23,390	22,823
Shares used in basic net (loss) income per share calculation (in thousands)	23,525	22,937	23,390	22,823
Effect of dilutive securities (in thousands)	0	193	0	117
Denominator for diluted net (loss) income per share (in thousands)	23,525	23,130	23,390	22,940
Basic net (loss) income per share	$ (0.03)	$ 0.01	$ (0.11)	$ 0
Diluted net (loss) income per share	$ (0.03)	$ 0.01	$ (0.11)	$ 0