One step at a time. Don't do anything until you've thoroughly researched it all. It's hard here as a farang, and many fail and become incredibly bitter and disillusioned.
I would just fly in - choose your airport wisely - take your chances with the immigration officer and hope for the best. I would dress up, and also have a printed copy of your return flights. It is a risk, but in the absence of the correct visa, it always would have been - but you knew that I'm sure. Good luck.