What should I do after my non-immigrant ED visa expires in Thailand and can I apply for a tourist visa immediately afterward?

Good morning :)

I'm on a non-immigrant-ED visa in Chiang Mai. My visa will expire 31st May but my study at CMU will be officially over around middle of May. I believe they will give me a paper which exactly states the day when I'm not a student anymore and I need to cancel my visa on that exact day (or before)?

Will I get a tourist visa just after canceling my ED Visa? Or do I have to leave the country on the same day and come back in to get a 30 day visa on arrival with German passport?

I hope you can make sense out of my writing ^^

Thank you for every help :)