10. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details 6) $ / shares in Units, $ in Thousands	12 Months Ended
	May 31, 2018 USD ($) $ / shares shares
Options exercisable and expected to be exercisable | shares	2,312,000
Weighted Average Exercise Price Exercisable | $ / shares	$ 1.89
$0.59-$0.97
Number of Options Outstanding, Ending | shares	299,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	9 months 7 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ .67
Options exercisable and expected to be exercisable | shares	299,000
Weighted Average Remaining Contractual Life (Years) Options Exercisable	9 months 7 days
Weighted Average Exercise Price Exercisable | $ / shares	$ .67
$1.09-$1.36
Number of Options Outstanding, Ending | shares	557,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	1 year 7 months 20 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.28
Options exercisable and expected to be exercisable | shares	556,000
Weighted Average Remaining Contractual Life (Years) Options Exercisable	1 year 7 months 20 days
Weighted Average Exercise Price Exercisable | $ / shares	$ 1.28
$1.68-$2.06
Number of Options Outstanding, Ending | shares	483,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 2 months 23 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.74
Options exercisable and expected to be exercisable | shares	314,000
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 8 months 23 days
Weighted Average Exercise Price Exercisable | $ / shares	$ 1.78
$2.10-$2.81
Number of Options Outstanding, Ending | shares	1,257,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 8 months 5 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.45
Options exercisable and expected to be exercisable | shares	1,073,000
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 5 months 26 days
Weighted Average Exercise Price Exercisable | $ / shares	$ 2.47
$3.46-$3.93
Number of Options Outstanding, Ending | shares	263,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	6 years 1 month 28 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 3.86
Options exercisable and expected to be exercisable | shares	70,000
Weighted Average Remaining Contractual Life (Years) Options Exercisable	6 years 2 months 16 days
Weighted Average Exercise Price Exercisable | $ / shares	$ 3.77
$0.59-$3.93
Number of Options Outstanding, Ending | shares	2,859,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 3 months 18 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.04
Options exercisable and expected to be exercisable | shares	2,312,000
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 9 months 22 days
Weighted Average Exercise Price Exercisable | $ / shares	$ 1.89
Aggregate Intrinsic Value | $	$ 1,778