@Tod ********
Desk is open 24 hours. At the far end of the immigration counters is the desk. Sometimes it is not manned, but just tell an officer you need a re-entry permit and they’ll get someone to help.
You don’t need anything other than your passport. They’ll do the forms and photos etc and charge you an additional service fee. I’ve heard reports that this is 500 baht on top of the 1,000 baht fee. They will only do single entry re-entry permits.