SHAREHOLDERS' EQUITY (Details) - USD ($)	12 Months Ended
May 31, 2017	May 31, 2016
SHAREHOLDERS' EQUITY (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$ 1.55	$ 1.17
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 616,000	$ 256,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	1,354,000	952,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	616,000	$ 542,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 36,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 266 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	5 years 113 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in Shares)	341,500	269,625
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit (in Dollars per share)	$ 0.43	$ 0.38
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit (in Dollars per share)	$ 1.04	$ 0.84
Proceeds from Stock Options Exercised	$ 157,728	$ 109,936
1999 Plan [Member]
SHAREHOLDERS' EQUITY (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	1,000,000
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Annual Increment Threshold Percentage	1.50%
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Annual Increment Threshold Number (in Shares)	500,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	80.00%
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
2010 Plan [Member]
SHAREHOLDERS' EQUITY (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	850,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	80.00%
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
2014 Plan [Member]
SHAREHOLDERS' EQUITY (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	850,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	80.00%
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years

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The annual increment in number of shares in accordance with the number of shares authorized under the plan.

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No definition available.

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The threshold percentage of annual increment in the number shares authorized under the plan.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Purchase price of common stock expressed as a percentage of its fair value.

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Number of share options (or share units) exercised during the current period.

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