STOCK-BASED COMPENSATION (Details Narrative) - USD ($)	3 Months Ended		9 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021
Total intrinsic values of options exercised	$ 867,000	$ 57,000	$ 11,902,000	$ 151,000
RSUs granted	0	4,000	169,000	165,000
Shares withheld for taxes and not issued		4,000	40,000	4,000
Market value on the date of the grant		$ 2.25	$ 2.98	$ 1.87
RSUs fully vested	21,000	19,000	50,000	34,000
RSUs unvested	475,000	143,000	475,000	143,000
Intrinsic value of RSUs, nonvested	$ 6,460,000	$ 400,000	$ 6,460,000	$ 400,000
Weighted average contractual life of the options exercisable and expected to be exercisable			4 years 14 days	3 years 8 months 4 days
Employee Stock Purchase Plan
Unrecognized stock-based compensation	648,000		$ 648,000
Weighted average period for recognition of costs			1 year
Stock-based compensation related to the ESPP	$ 364,000	$ 18,000	$ 770,000	$ 62,000
ESPP purchase right granted	0	0	103,000	81,000
ESPP shares issued			75,000	72,000
ESPP Shares available for issuance	361,000	511,000	361,000	511,000
Board Of Directors
RSUs granted	0	34,000	43,000	126,000
Market value on the date of the grant		$ 2.25	$ 8.02	$ 1.73
RSUs fully vested			33,000
RSUs unvested	10,000		10,000
Intrinsic value of RSUs, nonvested	$ 136,000		$ 136,000
RSU - Performance [Member]
RSUs unvested	270,000		270,000
Stock-based compensation expenses	$ 278,000		$ 524,000
Stock Option and RSU
Stock-based compensation expense related to stock options and RSUs	516,000	$ 253,000	1,416,000	$ 736,000
2016 Equity Incentive Plan
Unrecognized stock-based compensation	$ 1,915,000		$ 1,915,000
Weighted average period for recognition of costs			1 year 2 months 12 days