Note 5 - Accounts Receivable, Net, Contract Asset and Contract Liability (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2022	Jul. 31, 2021	Apr. 30, 2022
Accounts Receivable, after Allowance for Credit Loss, Total	$ 3,615		$ 3,636
Accounts Receivable, Allowance for Credit Loss, Ending Balance	205		205
Contract with Customer, Asset, after Allowance for Credit Loss, Total	1,144		$ 1,470
Increase (Decrease) in Contract with Customer, Asset	(326)	$ 157
Increase (Decrease) in Contract with Customer, Liability	$ 3,344	$ (2,994)