Do I need to cancel my Education Visa if I leave Thailand early?

Okay I think people are confused (schools too) about leaving on an extension of stay without a re-entry permit (which does NOT officially cancel your extension, just stamps you out of the country) AND taking documentation from your school to the immigration office to cancel the extension then leave the country.

IF you just leave but have no intention to return here, you can just go stamp out at the airport. BUT if you're ever thinking you'll come back here, and especially if you're ever thinking you'd get another ED visa or Non-B visa (for employment) you need to go thru the official process of cancelling the current extension at the immigration office BEFORE you go and stamp out at the airport.

Failing to do that would cause you problems when you come back and go to get a long term visa/extension as the previous extension will have not been officially cancelled.

Now that this isn't what your school tells you to do is neither here nor there, this is the way it's done officially so you don't have problems in the future. Whether you follow that or not is totally up to you

Unless you would be never back in Thailand, get your extension canceled otherwise you may be charged for overstay later. Get the letter from the school saying the end date as on your departure date. You may not need to apply for a Covid extension if you are leaving in a few days.

You should go to the immigration office with the paperwork from the school saying you are no longer studying and that you want your extension of stay cancelled. Then, ask for a 60 day extension of stay based on unable to travel due to COVID-19.