Just got my first 30 day extension of stay on my tourist visa at Phuket Immigration (Phuket Road).
Open 08:30 - 12:00 (last ticket issued at 11:30) then 13:00 - 16:00.
Dress code enforced (people in front turned away).
Info required:
Passport
1900 bhat cash
Completed TM7 form
One passport photo
Signed photocopy of personal info page of passport
Signed photocopy of entry stamp in passport
Signed photocopy of visa in passport
Signed photocopy of departure card
Ticket issued at 11:29 š±. Passport returned just before 12:00. If you miss this you have to wait until 13:00.
(Sorry if everyone knows this, however might be useful for newbies like me!).