14. STOCK-BASED COMPENSATION (Details 5) $ / shares in Units, $ in Thousands	6 Months Ended
	Nov. 30, 2020 USD ($) $ / shares shares
$1.22-$1.34
Options outstanding, ending (in thousands) | shares	133
Weighted average remaining contractual life (years) options outstanding	6 years 6 months 18 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.27
Options exercisable shares, ending (in thousands) | shares	17
Weighted average remaining contractual life (years) options exercisable	6 years 5 months 16 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 1.25
$1.64-$1.86
Options outstanding, ending (in thousands) | shares	1,092
Weighted average remaining contractual life (years) options outstanding	5 years 3 months 11 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.70
Options exercisable shares, ending (in thousands) | shares	574
Weighted average remaining contractual life (years) options exercisable	4 years 7 months 20 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 1.69
$2.03-$2.46
Options outstanding, ending (in thousands) | shares	1,048
Weighted average remaining contractual life (years) options outstanding	3 years 5 months 23 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.21
Options exercisable shares, ending (in thousands) | shares	771
Weighted average remaining contractual life (years) options exercisable	3 years 7 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 2.19
$2.63-$2.81
Options outstanding, ending (in thousands) | shares	411
Weighted average remaining contractual life (years) options outstanding	10 months 24 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.71
Options exercisable shares, ending (in thousands) | shares	410
Weighted average remaining contractual life (years) options exercisable	10 months 17 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 2.71
$3.46-$3.93
Options outstanding, ending (in thousands) | shares	202
Weighted average remaining contractual life (years) options outstanding	3 years 7 months 28 days
Weighted average exercise price outstanding, ending | $ / shares	$ 3.86
Options exercisable shares, ending (in thousands) | shares	174
Weighted average remaining contractual life (years) options exercisable	3 years 7 months 28 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 3.85
$1.22-$3.93
Options outstanding, ending (in thousands) | shares	2,886
Weighted average remaining contractual life (years) options outstanding	3 years 11 months 12 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.16
Options exercisable shares, ending (in thousands) | shares	1,946
Weighted average remaining contractual life (years) options exercisable	3 years 1 month 20 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 2.29
Aggregate intrinsic value for options exercisable | $	$ 9