I have seen them stop everyone and XRay the suitcase.....My guess is, if your airplane lands at the same time as an airplane from China.

They're not really looking for tins of Spam, though, are they?

I guess not....but it is not that they never check. I guess cigarettes and Alcohol is their target. For narcotics they have Inspector Wuff.

Never seen a sniffer dog at Swampy in 15 years of travel.

That makes sense as Suvarnabhumi was opened September 2006.

Not from UK, but me and the Mrs. have brought back all kinds of personal use food stuff and other items back in suitcases (no alcohol or cigs though) and have never been stopped or questioned.

BTW, it was less expensive to pay the extra case/weight with the airline then sending it all back by US postal service. Plus no waiting for it to arrive here weeks later, less chance of it being lost, stolen, breakage, etc.