Note 3 - Accounts Receivable, Net, Contract Asset and Contract Liability (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021
Accounts Receivable, after Allowance for Credit Loss, Total	$ 3,636	$ 1,961
Accounts Receivable, Allowance for Credit Loss, Ending Balance	205	143
Contract with Customer, Asset, after Allowance for Credit Loss, Total	1,470	421
Increase (Decrease) in Contract with Customer, Asset	1,049	226
Increase (Decrease) in Contract with Customer, Liability	(4,978)	3,609
Contract with Customer, Liability, Revenue Recognized	$ 5,798	$ 2,189,000