3. REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019
Net sales	$ 1,683	$ 6,874	$ 3,695	$ 12,407
Systems
Net sales	171	3,027	972	5,961
Contactors
Net sales	773	3,046	1,400	4,696
Services
Net sales	739	801	1,323	1,750
Wafer-level
Net sales	1,251	6,335	2,810	11,161
Test During Burn-In
Net sales	$ 432	$ 539	$ 885	$ 1,246