10. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details 1) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights included in:
Total stock-based compensation	$ 996	$ 999	$ 1,016
Effect on net income (loss) per share, Basic	$ .05	$ .06	$ .08
Effect on net income (loss) per share, Diluted	$ .04	$ .06	$ .08
Cost Of Sales
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights included in:
Total stock-based compensation	$ 148	$ 91	$ 87
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	592	714	723
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	$ 194	$ 206