Gym In Bangkok?

Are there many weight training gyms in Bangkok?

Do they have air-con as I've heard it is quite warm out there?

Do you know how much they charge?

I've heard you can get performance enhancing drugs over the counter - is this true?

Wouldnt mind doing some muay thai out there if its not too expensive once I get out there.

I will be staying near a/the river but not sure where that is - any around there would be good.

Cheers.