How do I obtain a re-entry permit before leaving Thailand?

To obtain a re-entry permit in Thailand, you can do so at the airport before leaving the country. Specifically, go to the immigration desk marked 're-entry permit' before you get your passport stamped out. It is recommended to get the re-entry permit in advance at the immigration office where you obtained your visa extension for convenience. However, it is also available at Suvarnabhumi Airport for 1,200 THB for a single and 4,000 THB for a multiple entry, which doesn’t require additional documents. The process is generally quick, averaging about 15 minutes, but planning ahead is advisable to avoid potential delays.