SHAREHOLDERS` EQUITY (Details) - USD ($)	12 Months Ended
May 31, 2019	May 31, 2018
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Payment Arrangement, Expense	$ 151,224	$ 18,473
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$ 2.60	$ 3.63
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 364,000	$ 87,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	808,000	2,755,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	685,000	1,749,000
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 332,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	2 years 113 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	4 years 339 days
Proceeds from Stock Options Exercised	$ 121,790	27,436
Proceeds from Issuance of Common Stock	1,776,575	1,266,871
Research and Development Expense [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Payment Arrangement, Expense	3,714	2,486
General and Administrative Expense [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Payment Arrangement, Expense	143,299	14,613
Selling and Marketing Expense [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Payment Arrangement, Expense	$ 4,163	$ 1,223
Common Stock [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in Shares)	163,500	34,750
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in Dollars per share)	$ 0.71	$ 0.71
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in Dollars per share)	$ 1.04	$ 1.04
Proceeds from Stock Options Exercised	$ 121,790	$ 27,436
Sale of Stock, Number of Shares Issued in Transaction (in Shares)	625,677	342,088
Proceeds from Issuance of Common Stock	$ 1,847,662	$ 1,379,226
Sale of Stock, Consideration Received on Transaction	$ 1,776,575	1,275,933
Common Stock, Value, Subscriptions		$ 9,062
Common Stock [Member] \| Minimum [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Sale of Stock, Price Per Share (in Dollars per share)	$ 2.59	$ 3.73
Common Stock [Member] \| Maximum [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Sale of Stock, Price Per Share (in Dollars per share)	$ 4.16	$ 4.74
MEXICO
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Payment Arrangement, Expense	$ 49	$ 151
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
2017 Plan [Member]
SHAREHOLDERS` EQUITY (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	900,000
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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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Monetary value of common stock allocated to investors to buy shares of a new issue of common stock before they are offered to the public. When stock is sold on a subscription basis, the issuer does not initially receive the total proceeds. In general, the issuer does not issue the shares to the investor until it receives the entire proceeds.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for option under share-based payment arrangement.

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The cash inflow from the additional capital contribution to the entity.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Cash received on stock transaction after deduction of issuance costs.

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The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Number of shares authorized for issuance under share-based payment arrangement.

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

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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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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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