For unis you can change your tourist visa to ed visa but you must have to have 15 days to expire your tourist visa. And you can do it by yourself at the same day without any hassle if you have all the docs ready. Student must have to enroll at the university because after 90 days you have to be there with documents supporting that you were studying at the school or university. Thai language classes you have to leave if you're not from the big NES countries.

At chaengwatthana....

This is from a decent school. You can print it online, gather your papers, then go in and they check it all over. Hope this list helps.

The form is tm86. Not sure about visa exempt, tourist visa can be changed

If it is a real school, and you have 15 days left on your visa, you can. They do your paperwork at the school, make sure you've got everything you need, some unis even have a bus to get to Chaengwatthana. You bring the correct paperwork and they change it over. You can also go out of the country to do it but it's easier to go directly from the school

You can Change your tourist visa in chaengwattana immigration office showing proper documents and paying 2000thb. That would be for 3 months, at the 90 day report you gotta show up with your institute documents, registration copies/ transcripts and extend 90 more days.

Ty

I m curious, is it Thai calendar or English calender?