10. STOCK-BASED COMPENSATION - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Stock-based compensation expense by line item
Stock-based compensation expense	$ 658	$ 820
Cost of revenues
Stock-based compensation expense by line item
Stock-based compensation expense	56	67
Research and development
Stock-based compensation expense by line item
Stock-based compensation expense	290	386
Selling, general and administrative
Stock-based compensation expense by line item
Stock-based compensation expense	$ 312	$ 367