CASH, CASH EQUIVALENTS AND INVESTMENTS (Details) - USD ($)	Nov. 30, 2022	May 31, 2022
Total cash and cash equivalents	$ 18,874,000	$ 31,484,000
Cost [Member]
Cash equivalents:	15,201,000
Cash	3,673,000
Total cash and cash equivalents	18,874,000
Total cash, cash equivalents and investments	36,670,000
Cost [Member] | Money Market Funds [Member]
Cash equivalents:	11,228,000
Long-term investments:	80,000
Cost [Member] | US Treasury Securities [Member]
Cash equivalents:	3,973,000
Short-term Investments	17,716,000
Gross Unrealized Loss
Cash equivalents:	0
Cash	0
Total cash and cash equivalents	0
Total cash, cash equivalents and investments	6,000
Gross Unrealized Loss | Money Market Funds [Member]
Cash equivalents:	0
Long-term investments:	0
Gross Unrealized Loss | US Treasury Securities [Member]
Cash equivalents:	0
Short-term Investments	6,000
Estimated Fair Value [Member]
Cash equivalents:	15,201,000
Cash	3,673,000
Total cash and cash equivalents	18,874,000
Total cash, cash equivalents and investments	36,664,000
Estimated Fair Value [Member] | Money Market Funds [Member]
Cash equivalents:	11,228,000
Long-term investments:	80,000
Estimated Fair Value [Member] | US Treasury Securities [Member]
Cash equivalents:	3,973,000
Short-term Investments	$ 17,710,000