SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity - $ / shares	12 Months Ended
	May 31, 2017	May 31, 2016
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options granted, number of stock options	55,000
Options exercised, number of stock options	(341,500)	(269,625)
Price Range Per Share $0.38 - $0.85 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options outstanding, number of stock options		1,148,000
Options outstanding, weighted average exercise price		$ 0.60
Price Range Per Share $1.04 - $1.20 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options granted, number of stock options		345,000
Options granted, weighted average exercise price		$ 1.17
Price Range Per Share $0.38 - $0.84 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options exercised, number of stock options		(269,625)
Options exercised, weighted average exercise price		$ 0.41
Price Range Per Share $0.43 - $1.04 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options exercised, number of stock options	(341,500)
Options exercised, weighted average exercise price	$ 0.46
Options canceled or expired, number of stock options	(15,500)	(24,375)
Options canceled or expired, weighted average exercise price	$ 0.90	$ 0.74
Price Range Per Share $0.43 - $1.20 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options outstanding, number of stock options	1,199,000
Options outstanding, weighted average exercise price	$ 0.81
Options outstanding, number of stock options		1,199,000
Options outstanding, weighted average exercise price		$ 0.81
Price Range Per Share $1.52 - $1.61 [Member]
SHAREHOLDERS' EQUITY (Details) - Outstanding Stock Options Activity [Line Items]
Options granted, number of stock options	55,000
Options granted, weighted average exercise price	$ 1.55
Price Range Per Share $0.71 - $1.61 [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	897,000
Options outstanding, weighted average exercise price	$ 0.98