SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity - $ / shares	12 Months Ended
May 31, 2020	May 31, 2019
Exercise Price Range Per Share $0.71 - $3.90 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options outstanding, number of stock options		1,138,625
Options outstanding, weighted average exercise price		$ 1.65
Exercise Price Range Per Share $2.25 - $3.62 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options granted, number of stock options		558,000
Options granted, weighted average exercise price		$ 2.60
Exercise Price Range Per Share $0.71 - $1.04 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options exercised, number of stock options		(163,500)
Options exercised, weighted average exercise price		$ 0.76
Exercise Price Range Per Share $0.71 - $3.62 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options canceled or expired, number of stock options		(56,916)
Options canceled or expired, weighted average exercise price		$ 2.49
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
Options outstanding, number of stock options		1,476,209
Options outstanding, weighted average exercise price		$ 2.07
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
Options outstanding, weighted average exercise price
Options outstanding, number of stock options	1,789,251
Options outstanding, weighted average exercise price	$ 2.75

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