@Michael *******
and it is about ease of travel. Why wait until you are at the right departure tract (it has to be departure 2 at the Suvarnabhumi and if you exit at departure 4, you need to walk all the way to departure 2 !) it is about the easiness of living: When I apply for the 1-year extension, I also apply for the re-entry permit. It is done & dusted within 25 minutes, and I don't have to worry about it. I know reports from people who forgot to buy one at the airport, and their extensions became invalid