13. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details 5) $ / shares in Units, $ in Thousands	6 Months Ended
	Nov. 30, 2018 USD ($) $ / shares shares
$0.59-$0.97
Options Outstanding, Ending (in thousands) | shares	249
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 months 7 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ .66
Options exercisable shares, ending (in thousands) | shares	249
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 months 7 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ .66
$1.09-$1.28
Options Outstanding, Ending (in thousands) | shares	498
Weighted Average Remaining Contractual Life (Years) Options Outstanding	1 year 2 months 19 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.28
Options exercisable shares, ending (in thousands) | shares	498
Weighted Average Remaining Contractual Life (Years) Options Exercisable	1 year 2 months 19 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.28
$1.68-$2.06
Options Outstanding, Ending (in thousands) | shares	713
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 10 months 13 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.84
Options exercisable shares, ending (in thousands) | shares	344
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 6 months 11 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.77
$2.10-$2.81
Options Outstanding, Ending (in thousands) | shares	1,651
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 1 month 17 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.43
Options exercisable shares, ending (in thousands) | shares	1,143
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 1 month 17 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 2.45
$3.46-$3.93
Options Outstanding, Ending (in thousands) | shares	262
Weighted Average Remaining Contractual Life (Years) Options Outstanding	5 years 7 months 28 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 3.86
Options exercisable shares, ending (in thousands) | shares	114
Weighted Average Remaining Contractual Life (Years) Options Exercisable	5 years 8 months 19 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 3.76
$0.59-$3.93
Options Outstanding, Ending (in thousands) | shares	3,373
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 8 months 8 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.11
Options exercisable shares, ending (in thousands) | shares	2,348
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 7 months 10 days
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.98
Aggregate Intrinsic Value for Options exercisable, ending | $	$ 653