5. ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands		12 Months Ended
		May 31, 2019	May 31, 2018	May 31, 2019	May 31, 2018
Receivables [Abstract]
Accounts receivable, gross				$ 4,859	$ 2,860
Less: Allowance for doubtful accounts		$ (4)	$ (4)	0	(4)
Accounts receivable, net				$ 4,859	$ 2,856
Allowance for doubtful accounts, Beginning		4	61
Allowance for doubtful accounts, Additions charged to costs and expenses		0	4
Allowance for doubtful accounts, Deductions	[1]	(4)	(61)
Allowance for doubtful accounts, Ending		$ 0	$ 4

[1] Deductions include write-offs of uncollectible accounts, collections of amounts previously reserved, and releases of allowance for doubtful accounts credited to expense.