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?