2. REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Net sales	$ 22,291	$ 21,056	$ 29,555
Systems
Net sales	8,099	9,566	18,174
Contactors
Net sales	10,784	6,154	6,500
Services
Net sales	3,408	5,336	4,881
Wafer-Level
Net sales	19,768	14,618	13,080
Test During Burn-In
Net sales	$ 2,523	$ 6,438	$ 16,475