You can get a re-entry permit (not a visa ๐ ) at either Suvarnabhumi or Don Mueang before you fly out. They are open
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To get re-entry permits for the "regular price" (1000baht single/3800baht multiple) You need copies of the data page of your passport, your current visa/extension, your most recent entry stamp and a passport sized photo
OR
You can pay 200baht more and just give them your passport (1200baht single/3800 baht multiple)
Tell the officer when you go to stamp out you want to buy a re-entry permit