SHAREHOLDERS' EQUITY (Tables)

12 Months Ended

May 31, 2020

Stockholders' Equity Note [Abstract]

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	NUMBER OF STOCK OPTIONS	EXERCISE PRICE  RANGE PER SHARE	WEIGHTED AVERAGE EXERCISE PRICE
Options outstanding at May 31, 2018	1,138,625	$0.71-$3.90	$	1.65
Options granted	558,000	$2.25-$3.62	$	2.60
Options exercised	(163,500)	$0.71-$1.04	$	0.76
Options canceled or expired	(56,916)	$0.71-$3.62	$	2.49
Options outstanding at May 31, 2019	1,476,209	$0.82-$3.90	$	2.07
Options granted	517,500	$2.68-$8.18	$	4.47
Options exercised	(137,958)	$0.82-$3.90	$	1.64
Options canceled or expired	(66,500)	$0.85-$8.18	$	3.43
Options outstanding at May 31, 2020	1,789,251	$0.82-$8.18	$	2.75

Schedule of Nonvested Share Activity [Table Text Block]

	NUMBER OF SHARES	STOCK OPTIONS WEIGHTED AVERAGE AVERAGE GRANT DATE FAIR VALUE
Non-vested shares at May 31, 2019	769,584	$	2.49
Granted	517,500	$	4.47
Vested	(407,750)	$	2.25
Forfeited	(56,750)	$	3.55
Non-vested shares at May 31, 2020	822,584	$	3.78

Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block]

RANGE OF EXERCISE PRICES	NUMBER OUTSTANDING May 31, 2020	WEIGHTED AVERAGE REMAINING CONTRACTUAL LIFE IN YEARS	WEIGHTED AVERAGE EXERCISE PRICE	NUMBER EXERCISABLE AT MAY 31, 2020	WEIGHTED AVERAGE EXERCISE PRICE
$ 0.82-$1.04	276,000	4.44	$0.84	276,000	$0.84
$ 1.20-$ 2.81	1,072,500	7.57	$2.17	506,000	$1.71
$ 3.62-$ 8.18	440,751	7.62	$5.38	184,667	$3.87