This. But also... it doesn't really matter what passport you have. You can pretty much use ANY manual desks, even if it says 'THAI PASSPORTS' above it. It's not like the Immigration Bureau has one software/system to process foreigners, the other for citizens. I have used my foreign passport to exit/enter the country many times via the THA channel.

Now, that's not to say there aren't any officers around the waiting area whose sole job is to find out what your nationality is and boss you around. Your mileage can therefore vary.