I think Knobby may be referring to these guys, Bangkok Airport Limousine. 1250 baht for fast track service alone, 1090 baht if you book car service along with fast track. I used them on my very first ladyboy trip years ago because I didn't want to be standing in a long immigration line while badly jet lagged. I haven't had need for them since, but it all went off without a hitch when I used them. It was very efficient and fast. They are not a dodgy outfit, they've been around a long time. Their car service was solid also. Spotless cars driven by sane drivers with good English skills.
https://www.limousine.in.th/fast-track-immigration.php
