The Westin Banyan Tree is certainly nice. It's on Sathorn Road.

(If the taxi driver doesn't know it, it may be a good idea just to say 'Sukhothai Hotel' and then as you approch Sukhothai, the Westin comes into view.)

It's pretty much available at 100USD range almost all the time. They also have a Pinnacle Club membership card, which includes a one-night stay and gives you 50% discount on the entire bill whenever you eat at the hotel with another person. It's something like 4,400 bahts. Membership is valid for one year.