For high end accomodation, the best value for money would be the Sofitel Silom, IMHO:
Hotel Sofitel Silom Bangkok - Luxury hotel BANGKOK - Official Web Site
It's the only 4/5 star hotel, I have ever stayed at in Bangkok, but I did do a lot of research beforehand. Using asiaroomdirect.com (or something like that), I got a standard room (very nice), for 3,500 baht per night. It's been a few years though. Since then, I have heard of people actually buying beds from the hotel (they are that nice), and shipped to their country.
As for ST though, it is not GF. A high end freelancer from CM2 or Spasso's will pass through easily, but not a standard gogo dancer or bargirl from Patpong unfortunately...