If I was to enter Thailand on a 60 day SETV, how soon after my arrival can I go to my local Immigration office for a 30 day extension? I would hope to extend it ASAP to give myself lots of time to go to BKK and renew my UK passport as I've got just 5 blank pages left. Could I for example, fly into Chiang Mai one day on a SETV and then on the next working day get a 30 day entension at my local Immigration office?
TLDR : Answer Summary
If you enter Thailand on a 60-day SETV, you can apply for a 30-day extension at your local Immigration office as soon as you have 45 days or less remaining on your current admission stamp. Therefore, you may have to wait a couple of weeks after your arrival before applying for the extension.