CASH, CASH EQUIVALENTS AND INVESTMENTS (Details) - USD ($)	Feb. 28, 2023	May 31, 2022
Total cash and cash equivalents	$ 17,188,000	$ 31,484,000
Gross Unrealized Loss
Cash equivalents:	0
Cash	0
Total cash and cash equivalents	0
Total cash, cash equivalents and investments	22,000
Cost [Member]
Cash equivalents:	15,709,000
Cash	1,479,000
Total cash and cash equivalents	17,188,000
Total cash, cash equivalents and investments	42,937,000
Estimated Fair Value [Member]
Cash equivalents:	15,709,000
Cash	1,479,000
Total cash and cash equivalents	17,188,000
Total cash, cash equivalents and investments	42,915,000
US Treasury Securities [Member] | Gross Unrealized Loss
Cash equivalents:	0
Short-term Investments	22,000
US Treasury Securities [Member] | Cost [Member]
Cash equivalents:	3,983,000
Short-term Investments	25,599,000
US Treasury Securities [Member] | Estimated Fair Value [Member]
Cash equivalents:	3,983,000
Short-term Investments	25,577,000
Money Market Funds [Member] | Gross Unrealized Loss
Cash equivalents:	0
Long-term investments:	0
Money Market Funds [Member] | Cost [Member]
Cash equivalents:	11,726,000
Long-term investments:	150,000
Money Market Funds [Member] | Estimated Fair Value [Member]
Cash equivalents:	11,726,000
Long-term investments:	$ 150,000