Hope this helps others.

We are from the UK and we’re went to Vietnam so was unable to get a visa at short notice so we landed in Bangkok on the 2nd July, passport was stamped for 30 days. We want to stay longer so we thought we would go to the Immigration Government Building in Bangkok but it was the wrong place. We were told to go to the IT Square Laksi Plaza and go to the 3rd floor. Link below.

We had to fill out 3 forms which they gave us and you need to have a photocopy of your passport and the page that had the stamp of when you arrived plus a passport photo that they can stick onto the form. They didn’t ask any questions we paid 1900 TB. That was it we now have 60 days in Thailand. It took about 2 hours in total and they shut for lunch between 12 and 1 so we had lunch on the ground floor. You can get an appointment booked online but they get booked up. They do have a photocopier and a photo place in the waiting area. We are so chuffed that we have managed to get 60 days.