4. FAIR VALUE MEASUREMENT (Tables)

12 Months Ended

May 31, 2018

Fair Value Disclosures [Abstract]

Fair value by hierarchy

    The following table summarizes the Company’s financial assets measured at fair value on a recurring basis as of May 31, 2018 (in thousands):

	Balance as of
	May 31, 2018		Level 1		Level 2		Level 3
Money market funds	$	7,733	$	7,733	$	—	$	—
U.S. Treasury securities		5,983		5,983		—		—
Certificate of deposit		80		—		80		—
Assets	$	13,796	$	13,716	$	80	$	—

    The following table summarizes the Company’s financial assets measured at fair value on a recurring basis as of May 31, 2017 (in thousands):

	Balance as of
	May 31, 2017		Level 1		Level 2		Level 3
Money market funds	$	15,516	$	15,516	$	—	$	—
Certificate of deposit		50		—		50		—
Assets	$	15,566	$	15,516	$	50	$	—