Can I extend my Ed Visa by doing a land crossing before it expires?

Somebody on an ED visa extension was just denied exiting the country at Mae Sai for a 30-day Visa exempt entry because they hadn't cancelled their ED visa extension before trying to leave.

IMPORTANT thing to remember is BEFORE you leave Thailand - cancel your extension of stay based on your ED visa.

I myself, Aussie, didn’t know of this fact until after the wise Tod explained that if you don’t cancel your previous extension of stay (before you leave Thailand), you can still be considered to be on “overstay” even though you return and are admitted back into the country on a new visa. Leaving Thailand doesn’t automatically cancel your previous extension of stay. Seems weird and illogical but if you don’t do it - you face a fine up to 20,000 Baht when you next go to extend your stay on your new visa.

Simply get a letter from your school requesting to cancel your extension of stay on the day you are planning to leave Thailand. Go to immigration and cancel, then leave on that day.

You won't get an Extension of Stay at a border crossing. If you go out and come back you will get a 30 day Visa Exempt Entry stamp.