Originally Posted by dsquared37

All exchange rates in the airport are set by AoT with the exception of the services offered on the lower level in the Airport Link area. There is Superich (green) and also (orange) as well as Value+ and other companies. With the exception of this one area rates throughout the airport will be depressed by >5% (usually about 2 THB /USD below market rates).

I've been using Superich (green) for years with no problems.

The main branch will give you a slightly better rate but unless you're exchanging a large sum or will be situated proximal to Ratchaprasong there's little reason to venture to the main branch.