2. STOCK-BASED COMPENSATION - Compensation costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014	Aug. 31, 2013
Stock-based compensation in the form of employee stock options and ESPP shares included in:
Total stock-based compensation	$ 197	$ 143
Cost Of Sales
Stock-based compensation in the form of employee stock options and ESPP shares included in:
Total stock-based compensation	14	8
Selling, General and Administrative
Stock-based compensation in the form of employee stock options and ESPP shares included in:
Total stock-based compensation	148	104
Research And Development
Stock-based compensation in the form of employee stock options and ESPP shares included in:
Total stock-based compensation	$ 35	$ 31