If you have a work permit or any kind of one-year visa in Thailand and you want to leave the country on a business trip, holiday or for any other reason, you must get a re-entry permit. A re-entry permit basically gives you permission to leave Thailand and ‘re-enter’ without losing your visa or non-imm B (work permit visa). If you do not get a re-entry permit stamped in your passport and try to re-enter the country without it, you will lose your visa and your work permit and have to re-apply for both.
Up until recently, it was impossible to get a re-entry permit at Suvarnabhumi Airport in Bangkok, so you had to go to an immigration department a few days before your trip to apply for one. Not anymore. Now, you can get re-entry permits at Suvarnabhumi Airport on the same day as your flight.
To get a re-entry permit at Suvarnabhumi Airport, you need to apply at the small booth they have set up for the purpose. You’ll find this at the end of the airport (on the right-hand side, if you stand facing the front of the building), but there are large signs directing you there, so it’s easy to find.
To apply for a re-entry permit you will need 1,200 baht ($40), and, no, they are not cheap, as well as photocopies of the photograph page of your passport and photocopies of the page where your current visa is. While they usually only need one photocopy of each, I always take two copies as I was once asked for them.
You will also need a passport-sized photograph, or you can pay to have the photo taken there, and you must already have your boarding pass.
You do need to get to the airport well in advance of your flight if you need a re-entry permit, as it can take a while depending on how many people are in line in front of you. I got one on Saturday before I left Thailand, and it took just about an hour. The last time I applied for one, it took closer to an hour and a half, so I’d recommend getting there about 4 hours before your flight. Drop off the application form and go and enjoy a nice coffee or eat lunch at the cheap food court at Suvarnabhumi.