2. REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Net sales	$ 16,600	$ 22,291	$ 21,056
Systems
Net sales	7,250	8,099	9,566
Contactors
Net sales	5,837	10,784	6,154
Services
Net sales	3,513	3,408	5,336
Wafer-Level
Net sales	15,004	19,768	14,618
Test During Burn-In
Net sales	$ 1,596	$ 2,523	$ 6,438