17. SELECTED QUARTERLY CONSOLIDATED FINANCIAL DATA (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2018	May 31, 2017	May 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 7,269	$ 7,393	$ 7,923	$ 6,970	$ 6,683	$ 2,681	$ 4,216	$ 5,318	$ 29,555	$ 18,898	$ 14,501
Gross profit	3,161	3,176	3,131	2,918	2,608	503	1,463	2,206	12,386	6,780	5,145
Net income (loss)	$ 191	$ 267	$ 60	$ 10	$ (795)	$ (2,651)	$ (1,452)	$ (755)	$ 528	$ (5,653)	$ (6,785)
Net income (loss) per share basic and diluted	$ 0.01	$ 0.01	$ .00	$ .00	$ (0.04)	$ (0.16)	$ (0.09)	$ (0.06)	$ 0.02	$ (0.35)	$ (0.52)