Although it still states on the Thai Immigration website that the issue of re-entry permits is at the discretion of the immigration officer, a "new" service is now being offered prior to passport control. I had to make use of this service when my local immigration office was closed on 10th of April for a special holiday. In a panic I phoned the 1111 number to ask if it was possible, given the special circumstances, to get the permit at the airport. I was told it was, and to arrive very early, have my TM 8 filled out, a 2 inch photo and copies of my passport and work permit.
I arrived with all the required documents and checked in for my flight about four hours before its departure. then I went to look for the place to do the permit. As it was it couldn't have been easier. There is a special desk at passport control 2 - and I didnt need any documents either. The man waved away my completed TM8 and filled it in for me on computer, then took my photo - all I had to do was sign. He then took it to the immigration officer and got my permit stamp, all in about 10 minutes.
This service is offered for a fee of 200 Baht plus the 1000 for the permit, and is available at passport control 2 from 06.00 - 24.00, and you have to have already checked in for your flight. You can then either go through passport control or head back outside!