I entered Thailand 12 years ago on a non-b. Then switched to tourist visas, then converted a tourist visa into an education visa some years ago. That tourist visa would have been from Laos
I've been on an Ed visa for the past 5 years with a legitimate Thai University. I last left and reentered Thailand from Vietnam at Don mueang December 2017 with a reentry permit for the Ed visa. I canceled my Ed visa just a few months ago before jumping onto a covid visa.
Unfortunately, the day you graduate you must cancel your visa or incur an overstay, hence jumping off of my Ed visa.