I was just scoping out rates for Bangkok myself. Check out the Leading Hotels website. www.LHW.com

There are some rates at the Pen for $140 (US) per night. It may not be as out of reach as you think.

If you go this route, I may add that on Travelocity you can sign up for the "Leaders Club" for $79. Supposedly "exclusive" for frequent high dollar stayers at LHW properties - yet oddly enough available for a cost through Travelocity, it can net upgrades, etc. But do a more thorough FT search on this before you drop the $79.