Here are some websites that are worth looking at:
Gym Websites
http://www.rawaimuaythai.com/khaolakgym/
http://www.muaythaichinnarach.com
My friend Alan stayed at Sinbi, and said it was excellent.
“(I) stayed in Sinbi apartments about 5 mins away from gym lovely place private pool and gated, you can stay at the gym as well it’s a lot cheaper and all accommodation is very clean and good”