Note 4 - Stock-based Compensation - Summary of Stock-based Compensation by Income Statement Line Item (Details) - USD ($) $ in Thousands	3 Months Ended
Aug. 26, 2018	Aug. 27, 2017
Stock-based compensation expense	$ 728	$ 950
Cost of Sales [Member]
Stock-based compensation expense	101	124
Research and Development Expense [Member]
Stock-based compensation expense	25	20
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense	602	806
Employee Stock Option [Member]
Stock-based compensation expense	221	324
Restricted Stock Units (RSUs) [Member]
Stock-based compensation expense	$ 507	$ 626

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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