I was told last time to "go to shop near Hospital" to get photocopies.
I first went to the Patong office a few years ago and was in and out within 5 minutes. Brilliant!
Last time, back in November, I thought I was prepared (form filled in, photo, etc) but didn't have photocopies of the passport photo page / page with stamp in it. The office was almost empty. I came back a couple of days later and it was packed. So I came back the week after for a third time and got it sorted. But I had to come back an hour later to pick up my passport. So not a great experience.
Tip: don't go on a Monday or Friday as very likely to be busy.