This, I didn't have a contract with my clients too, just create 2 on the spot and sent them to sign (they embassy request to be signed by both parties).
Asking the gyms is you best option, there are many posts here, one guy posted today that their schedule is 1 training a week, but you can do more, just have to see with each gym (1 training a week feels almost useless, when I used to train I did 3 a week at least but I was not in Thailand and I had a full-time job)
Many embassies, if not all, say 3 months before departure and not earlier that 1 month.
I applied in October and our flight is in February 2025, they were ok with that, but depends from the embassy, contact them and ask, I wrote to them and got this reply:
Anonymous participant They asked me too in Prague (via email not like that on the online submission), I printed everything for nothing, they had already all the documents submitted printed, so we had the same stuff 2 times, and it was a lot of stuff like 50 pages, but better print it anyway, each embassy is a story on its own.