I have a Muay Thai gym in Bangkok, and if you are living in Hua Hin it probably makes sense to choose somewhere close to where you live, you might want to look at more options in Hua Hin.
Our gym is called Tiger Eye and feel free to see our reviews in this group.
Tiger Eye. I happen to be the owner so you can feel free to ask me any questions and if for whatever reason you want to try another gym I'm more than happy to give my recommendation. I've been in the Martial Arts industry for a long time.
For full transparency I own a Muay Thai gym in Bangkok.
We had students apply in HCMC and normally it's been a quick and easy process but there was a week where two students got additional requests that didn't make any sense. They resubmitted and got approved, after that one week things seemed to be back to normal.