10. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details 1) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2017
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights included in:
Total stock-based compensation	$ 905	$ 996	$ 999
Effect on net income (loss) per share, Basic	$ .04	$ 0.05	$ 0.06
Effect on net income (loss) per share, Diluted	$ .04	$ 0.04	$ 0.06
Cost Of Sales
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights included in:
Total stock-based compensation	$ 104	$ 148	$ 91
Selling, General and Administrative
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights included in:
Total stock-based compensation	545	592	714
Research And Development
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights included in:
Total stock-based compensation	$ 256	$ 256	$ 194