If you are wanting to claim the tourist VAT 7% Tax Refund you need to go to the Customs Office located near to Check in desk 5 in Terminal #1, to get your VAT receipt stamped.
Before you go through immigration.
If you don't have too many bags I would do this before you even check in.
I recently bought a lap top in Bangkok and asked the dealer for the 7% tax return. He got the paperwork sorted out, all stamped correctly and so I was eligble for nearly a B3000 VAT refund. You have 60 days to collect your refund at the airport as you are leaving.
I checked in, bought my airport tax voucher and went to immigration. It was packed with about 20 people in each immigration queue.
After half an hour I got to the desk and I see a printed A4 note saying that if I wanted the VAT refund I had to get my paper work stampled in the customs office before the check in desks.
Immigration smiled politely and informed me no stamp no refund.
So I went back out of immigration I had to get a counter signature on my Airport tax voucher, and then go around all the check in desks to find the Customs office. I just showed my passport and the receipt and it was all done in 5 minutes, they weren't interested in the lap top.
So all the way back to immigration - it was just as busy so another 30 minutes wait in the queue. I finally get into the departure lounge and found the VAT refund desk and was refunded the VAT within 5 minutes.
Two other people were refused the refund as they didn't have the required customs stamp.
Fortunately I had arrived a bit early at the airport, so I managed to claim it back and make my flight. Otherwise I would have said &%*^ it and not bothered.
But why was there no information on this until the immigration desk, it would help if they told you while you are checking in. Or maybe they don't want you to claim ..................