Work Permit/Extension OF Stay:
So when I leave the country without a re entry permit, my extension of stay in automtically cancelled, right?
My school will cancel my work permit/extension of stay hopefully the day I leave or the day after.
Say I booked a return flight into Thailand on the same day and tried to enter on a Visa Exempt but my school hadn't cancelled my work permit yet......
I wouldn't have a problem, right?
The problem only occurs if you are trying to get a new work permit but my school would cancel the work permit the next day anyway
TLDR : Answer Summary
When leaving Thailand without a re-entry permit, your extension of stay is automatically canceled. Your employer can only cancel your work permit when they have your passport. If you return on the same day without having your work permit canceled, you may enter on a Visa Exempt without issue, but be aware of potential fines for not canceling your extension properly if you apply for a new work permit later. Overstay fines are applicable based on the cancellation date of your work permit.