in other words "a proper visa" = any visa that you applied for and got from either a thai embassy/consulate, or bought from immigration inside Thailand after already entering.
They don't sell visa at the airport other than for a few countries that have to buy visa on arrival, 14 days visa only.
Those do not apply to you, because of your nationality
Instead they will let you in for free, for 30 days, with no visa at all. But only for so many times if you keep doing it back to back.
it doesn't have to be a long term visa. But an actual visa. One that you apply for, pay for, and receive, before you even leave your home country. Or in some cases that you buy at immigration inside Thailand. You can't get a tourist visa inside Thailand though. Only long term visas of different kinds
an exemption stamp is per definition not a visa. It's a granted entry without visa, aimed at tourists. But you do you. Some people can use those lots of times. Even back to back. Other people will get pulled aside and questioned only after a few times. All will eventually get denied entry if they keep doing that.
that depends what kind of ed visa. If from some shady language school performing as a visa factory, then yes. Immigration knows what's up with that and will possibly deny changing to other visa types after.
Having had an ed visa from a respected uni? No problem whatsoever.