STOCK-BASED COMPENSATION (Details 4) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Feb. 28, 2022 USD ($) $ / shares shares
$1.22-$1.34
Options outstanding, ending (in thousands) | shares	51
Weighted average remaining contractual life (Years) options outstanding	5 years 7 months 20 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.34
Option exercisable shares (in thousands) | shares	51
Weighted average remaining contractual life (Years) options exercisable	5 years 7 months 20 days
Weighted average exercise price for options exercisable | $ / shares	$ 1.34
$1.64-$1.86
Options outstanding, ending (in thousands) | shares	671
Weighted average remaining contractual life (Years) options outstanding	4 years 3 months 7 days
Weighted average exercise price outstanding, ending | $ / shares	$ 1.71
Option exercisable shares (in thousands) | shares	387
Weighted average remaining contractual life (Years) options exercisable	3 years 10 months 20 days
Weighted average exercise price for options exercisable | $ / shares	$ 1.69
$2.03-$2.46
Options outstanding, ending (in thousands) | shares	547
Weighted average remaining contractual life (Years) options outstanding	3 years 1 month 17 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.23
Option exercisable shares (in thousands) | shares	447
Weighted average remaining contractual life (Years) options exercisable	2 years 11 months 1 day
Weighted average exercise price for options exercisable | $ / shares	$ 2.23
$2.63-$2.93
Options outstanding, ending (in thousands) | shares	223
Weighted average remaining contractual life (Years) options outstanding	5 years 10 months 13 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.92
Option exercisable shares (in thousands) | shares	47
Weighted average remaining contractual life (Years) options exercisable	4 years 3 days
Weighted average exercise price for options exercisable | $ / shares	$ 2.86
$3.46-$3.93
Options outstanding, ending (in thousands) | shares	104
Weighted average remaining contractual life (Years) options outstanding	2 years 5 months 1 day
Weighted average exercise price outstanding, ending | $ / shares	$ 3.84
Option exercisable shares (in thousands) | shares	104
Weighted average remaining contractual life (Years) options exercisable	2 years 5 months 1 day
Weighted average exercise price for options exercisable | $ / shares	$ 3.84
$9.94-$19.85
Options outstanding, ending (in thousands) | shares	12
Weighted average remaining contractual life (Years) options outstanding	6 years 8 months 8 days
Weighted average exercise price outstanding, ending | $ / shares	$ 16.54
Option exercisable shares (in thousands) | shares	1
Weighted average remaining contractual life (Years) options exercisable	6 years 7 months 24 days
Weighted average exercise price for options exercisable | $ / shares	$ 19.46
$1.22-$19.85
Options outstanding, ending (in thousands) | shares	1,608
Weighted average remaining contractual life (Years) options outstanding	4 years 14 days
Weighted average exercise price outstanding, ending | $ / shares	$ 2.29
Option exercisable shares (in thousands) | shares	1,037
Weighted average remaining contractual life (Years) options exercisable	3 years 5 months 1 day
Weighted average exercise price for options exercisable | $ / shares	$ 2.19
Aggregate intrinsic value for options exercisable | $	$ 11,831