12. STOCK-BASED COMPENSATION (Details 4) $ / shares in Units, $ in Thousands	6 Months Ended
	Nov. 30, 2019 USD ($) $ / shares shares
$1.09-$1.28
Options outstanding, ending (in thousands) | shares	260
Weighted average remaining contractual life (years) options outstanding	6 months 25 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.28
Options exercisable shares, ending (in thousands) | shares	260
Weighted average remaining contractual life (years) options exercisable	6 months 25 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 1.28
$1.64-$2.06
Options outstanding, ending (in thousands) | shares	1,199
Weighted average remaining contractual life (years) options outstanding	5 years 6 months 11 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.76
Options exercisable shares, ending (in thousands) | shares	447
Weighted average remaining contractual life (years) options exercisable	4 years 2 months 19 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 1.81
$2.10-$2.81
Options outstanding, ending (in thousands) | shares	1,439
Weighted average remaining contractual life (years) options outstanding	3 years 1 month 17 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.43
Options exercisable shares, ending (in thousands) | shares	1,146
Weighted average remaining contractual life (years) options exercisable	2 years 5 months 23 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 2.43
$3.46-$3.93
Options outstanding, ending (in thousands) | shares	229
Weighted average remaining contractual life (years) options outstanding	4 years 7 months 28 days
Weighted average exercise price outstanding, ending | $ / shares	$ 3.85
Options exercisable shares, ending (in thousands) | shares	151
Weighted average remaining contractual life (years) options exercisable	4 years 8 months 8 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 3.80
$1.09-$3.93
Options outstanding, ending (in thousands) | shares	3,127
Weighted average remaining contractual life (years) options outstanding	3 years 11 months 12 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.18
Options exercisable shares, ending (in thousands) | shares	2,004
Weighted average remaining contractual life (years) options exercisable	2 years 9 months 15 days
Weighted average exercise price for options exercisable, ending | $ / shares	$ 2.25
Aggregate intrinsic value for options exercisable | $	$ 219