SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity - $ / shares	12 Months Ended
May 31, 2021	May 31, 2020
Exercise Price Range Per Share $0.82 - $3.90 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options outstanding, number of stock options		1,476,209
Options outstanding, weighted average exercise price		$ 2.07
Options exercised, number of stock options		(137,958)
Options exercised, weighted average exercise price		$ 1.64
Exercise Price Range Per Share $2.68 - $8.18 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options granted, number of stock options		517,500
Options granted, weighted average exercise price		$ 4.47
Exercise Price Range Per Share $0.85 - $8.18 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options canceled or expired, number of stock options		(66,500)
Options canceled or expired, weighted average exercise price		$ 3.43
Exercise Price Range Per Share $0.82 - $8.18 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options outstanding, number of stock options	1,789,251
Options outstanding, weighted average exercise price	$ 2.75
Options outstanding, number of stock options		1,789,251
Options outstanding, weighted average exercise price		$ 2.75
Exercise Price Range Per Share $5.14 - $8.70 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options granted, number of stock options	430,616
Options granted, weighted average exercise price	$ 6.73
Exercise Price Range Per Share $0.82 - $3.62 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options exercised, number of stock options	(86,750)
Options exercised, weighted average exercise price	$ 1.20
Exercise Price Range Per Share $2.35 - $8.18 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options canceled or expired, number of stock options	(51,751)
Options canceled or expired, weighted average exercise price	$ 4.77
Exercise Price Range Per Share $0.82 - $8.70 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options outstanding, number of stock options
Options outstanding, weighted average exercise price
Options outstanding, number of stock options	2,081,366
Options outstanding, weighted average exercise price	$ 3.59

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