2. STOCK-BASED COMPENSATION (Details 4) $ / shares in Units, $ in Thousands	3 Months Ended
	Aug. 31, 2017 USD ($) $ / shares shares
$0.59-$0.97
Options Outstanding, Ending (in thousands) | shares	454
Weighted Average Remaining Contractual Life (Years) Options Outstanding	1 year 6 months 14 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 0.67
Options exercisable shares, ending (in thousands) | shares	454
Weighted Average Remaining Contractual Life (Years) Options Exercisable	1 year 6 months 14 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 0.67
$1.09-$1.36
Options Outstanding, Ending (in thousands) | shares	688
Weighted Average Remaining Contractual Life (Years) Options Outstanding	2 years 3 months 25 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.27
Options exercisable shares, ending (in thousands) | shares	688
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 3 months 25 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.27
$1.68-$2.06
Options Outstanding, Ending (in thousands) | shares	516
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 10 months 24 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.75
Options exercisable shares, ending (in thousands) | shares	285
Weighted Average Remaining Contractual Life (Years) Options Exercisable	4 years 1 month 6 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.81
$2.10-$2.81
Options Outstanding, Ending (in thousands) | shares	1,227
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 3 months 7 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.44
Options exercisable shares, ending (in thousands) | shares	914
Weighted Average Remaining Contractual Life (Years) Options Exercisable	4 years 2 months 26 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 2.46
$3.93
Options Outstanding, Ending (in thousands) | shares	224
Weighted Average Remaining Contractual Life (Years) Options Outstanding	6 years 10 months 10 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 3.99
Options exercisable shares, ending (in thousands) | shares	5
Weighted Average Remaining Contractual Life (Years) Options Exercisable	6 years 10 months 10 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 3.99
$0.59-$3.93
Options Outstanding, Ending (in thousands) | shares	3,109
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 8 months 23 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.92
Options exercisable shares, ending (in thousands) | shares	2,346
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 1 month 20 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.69
Aggregate Intrinsic Value for Options exercisable, ending | $	$ 3,919