I haven't been to Don Muang airport for years, I have no idea about the location of the 're-entry' desk there.
No, the re-entry visa desk at BKK (Suv) is before the immigration desks. When you enter the immigration departure room, the immigration desks are in front of you while the re-entry visa desk is to the left in the corner. Go to that desk in the left hand corner of that room, present your paperwork and pay the fee and the immigration person will take it to her left, and you can sit in a chair while the re-entry visa is processed.