STOCK-BASED COMPENSATION (Details Narrative) - USD ($)	3 Months Ended		6 Months Ended
	Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Total intrinsic values of options exercised	$ 9,133,000	$ 3,000	$ 11,035,000	$ 95,000
Weighted average contractual life of the options exercisable and expected to be exercisable			4 years 2 months 19 days	3 years 11 months 4 days
RSUs granted	1,000		120,000	161,000
RSUs granted for bonus			49,000
Shares withheld for taxes and not issued on RSU for bonus			40,000
Market value on the date of the grant	$ 24.57		$ 2.98	$ 1.86
RSUs fully vested	18,000	11,000	29,000	14,000
RSUs unvested	237,000	155,000	237,000	155,000
Intrinsic value of RSUs, nonvested	$ 4,129,000	$ 256,000	$ 4,129,000	$ 256,000
Employee Stock Purchase Plan
Unrecognized stock-based compensation	1,012,000		$ 1,012,000
Weighted average period for recognition of costs			1 year
Stock-based compensation related to the ESPP	$ 302,000	$ 19,000	$ 406,000	$ 44,000
ESPP purchase right granted	103,000	72,000	103,000	72,000
ESPP shares issued	75,000	72,000	75,000	72,000
ESPP Shares available for issuance	361,000	161,000	361,000	161,000
Stock Option and RSU
Stock-based compensation expense related to stock options and RSUs	$ 416,000	$ 238,000	$ 900,000	$ 483,000
2016 Equity Incentive Plan
Unrecognized stock-based compensation	1,797,000		1,797,000
Estimated forfeitures of unvested stock based awards, amount	$ 5,000		$ 5,000
Weighted average period for recognition of costs			1 year 9 months 18 days
Board Of Directors
RSUs granted	13,000	57,000	43,000	92,000
Market value on the date of the grant	$ 19.85	$ 1.34	$ 8.02	$ 1.54
RSUs fully vested		57,000	30,000	92,000
RSU - Performance [Member]
RSUs unvested	270,000		270,000
Stock-based compensation expenses	$ 246,000		$ 246,000