18. SELECTED QUARTERLY CONSOLIDATED FINANCIAL DATA (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2019	May 31, 2018	May 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 7,242	$ 3,163	$ 5,911	$ 4,740	$ 7,269	$ 7,393	$ 7,923	$ 6,970	$ 21,056	$ 29,555	$ 18,898
Gross profit	3,379	272	2,398	1,553	3,161	3,176	3,131	2,918	7,602	12,386	6,780
Net (loss) income	$ 110	$ (3,201)	$ (629)	$ (1,515)	$ 191	$ 267	$ 60	$ 10	$ (5,235)	$ 528	$ (5,653)
Net (loss) income per share basic and diluted	$ .00	$ (0.14)	$ (0.03)	$ (0.07)	$ 0.01	$ 0.01	$ 0.00	$ 0.00	$ (0.23)	$ 0.02	$ (0.35)