Good gyms in Bangkok?

Hi everyone, not sure if this was the right forum to post this thread under, but here it is anyway!

I will be moving to Bangkok this June for work, and plan on staying around the On-Nut area for a while until I find a better place. I really want to get back into fitness by going to gym after work. The building I plan on living in already has a small gym, however I am trying to look for a gym with more facilities and equipment (mainly resistance equipment and weights).

I was wondering if anyone could give me advice on good gyms around the On Nut or Ekkamai area (where I'll be working). I'm preferably looking for a place with good weights equipment, that is relatively cheap, and that doesn't get too busy after 6PM? I know this may be a lot to ask for, but I'm keeping my fingers crossed :)

Thanks!