Gyms in Thailand are extremely variable in terms of their facilities. You’ll find everything from top of the range global chains to small run-down looking places that’ll make you feel like you’ve stepped back in time a few decades. English is not widely spoken to any great degree, but most people will speak a little and can certainly communicate the price, which is very often on display in any case.
The gyms ranged in price from 49 baht to 300 baht, with 80-100 baht being a normal price for a non-air-conditioned gym with half decent facilities. Expect to pay considerably more in upmarket clubs; for example, one Fitness First club wanted to charge me for 846 baht – for one day!
Check websites of large chains to see if they offer a free trial. Fitness First do offer a 3 day free trial on theirs, but whether this applies to residents only may vary from club to club. My advice would be to register for it and try your luck! Their facilities are on par with their Western clubs.
Currency approximation : US$1 = 31.5 baht, €1 = 36 baht, £1 = 41.7, AU$1 = 22.7 baht
at the time of writing.