What are the requirements for obtaining a Thai DTV visa for Muay Thai training?

Hi everyone, I’m planning to apply for a Thai DTV visa for Muay Thai and I have a few questions for people who have already gone through the process.

For those who applied, what did the embassy actually ask for ?

Was it a letter of invitation from a Muay Thai camp, or something more?

If it was a letter, what did it need to include exactly? For example, dates, training schedule, duration, payment details, etc.

I’ve also seen online that the invitation is supposed to come from a certified or officially registered camp, and not just any gym. Can anyone confirm if that’s really required?

Before the camp issued the invitation letter, did you have to sign any kind of agreement with them? Did you need to pay in advance or commit to a specific training package and for a specific duration ?

And finally, were you required to stay at the same camp for the entire duration of the DTV visa?

I’m asking because I’m not sure I want to stay in one place the whole time.

Thanks a lot in advance for your help.