STOCK-BASED COMPENSATION (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Total stock-based compensation	$ 718	$ 257	$ 1,306	$ 527
Cost of Sales
Total stock-based compensation	76	15	158	31
Selling, General and Administrative
Total stock-based compensation	377	194	772	399
Research and Development
Total stock-based compensation	$ 265	$ 48	$ 376	$ 97

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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