13. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Nov. 30, 2018

Equity [Abstract]

Changes in the components of AOCI

Changes in the components of AOCI, net of tax, were as follows (in thousands):

	Cumulative Translation Adjustments			Unrealized Loss on Investments, Net		Total
Balance at May 31, 2018	$	2,292		$	--	$	2,292
Other comprehensive (loss) income before reclassifications		(51	)		--		(51	)
Amounts reclassified out of AOCI		--			--		--
Other comprehensive (loss) income, net of tax		(51	)		--		(51	)
Balance at November 30, 2018	$	2,241		$	--	$	2,241

Compensation costs related to the Company's stock-based compensation

The following table summarizes the stock-based compensation expense for the three and six months ended November 30, 2018 and 2017 (in thousands):

	Three Months Ended				Six Months Ended
	November 30,				November 30,
	2018		2017		2018		2017
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights, included in:
Cost of sales	$	23	$	57	$	59	$	79
Selling, general and administrative		136		218		284		368
Research and development		65		89		137		133
Total stock-based compensation	$	224	$	364	$	480	$	580

Fair value assumptions for option valuation model

The fair value of the Company’s stock options granted to employees for the three and six months ended November 30, 2018 and 2017 were estimated using the following weighted average assumptions in the Black-Scholes option valuation model:

	Three Months Ended						Six Months Ended
	November 30,						November 30,
	2018			2017			2018			2017
Expected term (in years)		5			4			5			4
Volatility		0.70			0.74			0.72			0.77
Risk-free interest rate		3.01	%		1.92	%		2.84	%		1.77	%
Weighted average grant date fair value	$	1.21		$	1.93		$	1.38		$	2.22

The fair values of the ESPP purchase rights granted for the three and six months ended November 30, 2018 were estimated using the following weighted-average assumptions:

	Three and Six Months Ended
	November 30, 2018
Expected term (in years)	0.5-2.0
Volatility	0.48-0.64
Expected dividend	$0.00
Risk-free interest rates	2.40%-2.82%
Estimated forfeiture rate	0%
Weighted average grant date fair value	$1.15

Stock option and RSU transactions

The following tables summarize the Company’s stock option and RSU transactions during three and six months ended November 30, 2018 (in thousands):

	Available
	Shares
Balance, May 31, 2018		1,812
Options granted		(441	)
RSUs granted		--
Shares cancelled		13
Shares expired		(11	)
Balance, August 31, 2018		1,373
Options granted		(248	)
RSUs granted		--
Shares cancelled		45
Shares expired		(33	)
Balance, November 30, 2018		1,137

Stock option transactions

The following table summarizes the stock option transactions during the three and six months ended November 30, 2018 (in thousands, except per share data):

	Outstanding Options
				Weighted
	Number			Average		Aggregate
	of			Exercise		Intrinsic
	Shares			Price		Value
Balances, May 31, 2018		2,859		$	2.04	$	1,987
Options granted		441		$	2.40
Options cancelled		(13	)	$	1.64
Options exercised		(98	)	$	1.12
Balances, August 31, 2018		3,189		$	2.12	$	1,757
Options granted		248		$	2.03
Options cancelled		(45	)	$	2.70
Options exercised		(19	)	$	1.09
Balances, November 30, 2018		3,373		$	2.11	$	679
Options fully vested and expected to vest at November 30, 2018		3,337		$	2.11	$	678

Options outstanding

The options outstanding and exercisable at November 30, 2018 were in the following exercise price ranges (in thousands, except per share data):

	Options Outstanding at November 30, 2018					Options Exercisable at November 30, 2018
Range of Exercise Prices		Number Outstanding Shares	Weighted Average Remaining Contractual Life (Years)	Weighted Average Exercise Price		Number Exercisable Shares		Weighted Average Remaining Contractual Life (Years)	Weighted Average Exercise Price		Aggregate Intrinsic Value
$0.59-$0.97		249	0.27	$	0.66		249	0.27	$	0.66
$1.09-$1.28		498	1.22	$	1.28		498	1.22	$	1.28
$1.68-$2.06		713	4.87	$	1.84		344	3.53	$	1.77
$2.10-$2.81		1,651	4.13	$	2.43		1,143	3.13	$	2.45
$3.46-$3.93		262	5.66	$	3.86		114	5.72	$	3.76
$0.59-$3.93		3,373	3.69	$	2.11		2,348	2.61	$	1.98	$	653