5. FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Feb. 29, 2020	May 31, 2019
Assets
Investment securities	$ 80	$ 3,017
Level 1
Assets
Investment securities	80	3,017
Level 2
Assets
Investment securities	0	0
Level 3
Assets
Investment securities	0	0
Money Market Funds
Assets
Investment securities	80	3,017
Money Market Funds | Level 1
Assets
Investment securities	80	3,017
Money Market Funds | Level 2
Assets
Investment securities	0	0
Money Market Funds | Level 3
Assets
Investment securities	$ 0	$ 0