11. STOCKHOLDERS' EQUITY AND STOCK-BASED COMPENSATION (Details 5) $ / shares in Units, $ in Thousands	12 Months Ended
	May 31, 2021 USD ($) $ / shares shares
Option exercisable shares (in thousands) | shares	2,045
Weighted average exercise price for options exercisable | $ / shares	$ 2.26
$1.22-$1.34
Options outstanding, ending (in thousands) | shares	133
Weighted average remaining contractual life (Years) options outstanding	6 years 18 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.27
Option exercisable shares (in thousands) | shares	56
Weighted average remaining contractual life (Years) options exercisable	6 years 1 month 24 days
Weighted average exercise price for options exercisable | $ / shares	$ 1.29
$1.64-$1.86
Options outstanding, ending (in thousands) | shares	1,040
Weighted average remaining contractual life (Years) options outstanding	4 years 9 months 18 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.7
Option exercisable shares (in thousands) | shares	625
Weighted average remaining contractual life (Years) options exercisable	4 years 3 months 29 days
Weighted average exercise price for options exercisable | $ / shares	$ 1.69
$2.03-$2.46
Options outstanding, ending (in thousands) | shares	1,035
Weighted average remaining contractual life (Years) options outstanding	3 years 1 month 2 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.21
Option exercisable shares (in thousands) | shares	814
Weighted average remaining contractual life (Years) options exercisable	2 years 8 months 5 days
Weighted average exercise price for options exercisable | $ / shares	$ 2.2
$2.65-$2.81
Options outstanding, ending (in thousands) | shares	358
Weighted average remaining contractual life (Years) options outstanding	5 months 16 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.72
Option exercisable shares (in thousands) | shares	357
Weighted average remaining contractual life (Years) options exercisable	5 months 12 days
Weighted average exercise price for options exercisable | $ / shares	$ 2.72
$3.46-$3.93
Options outstanding, ending (in thousands) | shares	200
Weighted average remaining contractual life (Years) options outstanding	3 years 1 month 28 days
Weighted average exercise price outstanding, ending | $ / shares	$ 3.86
Option exercisable shares (in thousands) | shares	193
Weighted average remaining contractual life (Years) options exercisable	3 years 1 month 28 days
Weighted average exercise price for options exercisable | $ / shares	$ 3.85
$1.22-$3.93
Options outstanding, ending (in thousands) | shares	2,766
Weighted average remaining contractual life (Years) options outstanding	3 years 6 months 14 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.16
Option exercisable shares (in thousands) | shares	2,045
Weighted average remaining contractual life (Years) options exercisable	2 years 11 months 8 days
Weighted average exercise price for options exercisable | $ / shares	$ 2.26
Aggregate intrinsic value for options exercisable | $	$ 492