12. STOCK-BASED COMPENSATION (Details 3) - Outstanding Options Stock Option Transactions $ / shares in Units, $ in Thousands	3 Months Ended
	Aug. 31, 2019 USD ($) $ / shares shares
Options outstanding, beginning (in thousands) | shares	3,107
Options granted (in thousands) | shares	527
Options cancelled (in thousands) | shares	(151)
Options exercised (in thousand) | shares	(49)
Options outstanding, ending (in thousands) | shares	3,434
Weighted average exercise price outstanding, beginning | $ / shares	$ 2.20
Weighted average exercise price granted | $ / shares	1.64
Weighted average exercise price cancelled | $ / shares	1.50
Weighted average exercise price exercised | $ / shares	1.27
Weighted average exercise price outstanding, ending | $ / shares	$ 2.16
Aggregate intrinsic value, beginning balance | $	$ 282
Aggregate intrinsic value, ending balance | $	$ 41
Options fully vested and expected to vest, ending (in thousands) | shares	3,397
Weighted average exercise price for options fully vested and expected to vest, ending | $ / shares	$ 2.16
Aggregate intrinsic value for options fully vested and expected to vest, ending | $	$ 41