10. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details 6) $ / shares in Units, $ in Thousands	12 Months Ended
	May 31, 2019 USD ($) $ / shares shares
Option exercisable shares (in thousands) | shares	2,314
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ 2.14
$0.80-$0.97
Options Outstanding, Ending (in thousands) | shares	47
Weighted Average Remaining Contractual Life (Years) Options Outstanding	6 months 7 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ .85
Option exercisable shares (in thousands) | shares	47
Weighted Average Remaining Contractual Life (Years) Options Exercisable	6 months 7 days
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ .85
$1.09-$1.28
Options Outstanding, Ending (in thousands) | shares	456
Weighted Average Remaining Contractual Life (Years) Options Outstanding	9 months 11 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.28
Option exercisable shares (in thousands) | shares	456
Weighted Average Remaining Contractual Life (Years) Options Exercisable	9 months 11 days
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ 1.28
$1.65-$2.06
Options Outstanding, Ending (in thousands) | shares	761
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 6 months 25 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.83
Option exercisable shares (in thousands) | shares	427
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 6 months
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ 1.79
$2.10-$2.81
Options Outstanding, Ending (in thousands) | shares	1,600
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 6 months 18 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.43
Option exercisable shares (in thousands) | shares	1,244
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 9 months 22 days
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ 2.44
$3.46-$3.93
Options Outstanding, Ending (in thousands) | shares	243
Weighted Average Remaining Contractual Life (Years) Options Outstanding	5 years 1 month 28 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 3.85
Option exercisable shares (in thousands) | shares	140
Weighted Average Remaining Contractual Life (Years) Options Exercisable	5 years 2 months 12 days
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ 3.79
$0.80-$3.93
Options Outstanding, Ending (in thousands) | shares	3,107
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 5 months 19 days
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 2.20
Option exercisable shares (in thousands) | shares	2,314
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 7 months 20 days
Weighted Average Exercise Price for Options Exercisable | $ / shares	$ 2.14
Aggregate Intrinsic Value for Options Exercisable | $	$ 274