However, this place will still insist on making you show them your boarding card and passport before they sell you anything, including a bottle of water.
A British chap in front of me got highly incensed at this request, rightly suggesting it was merely a ruse to claim back the VAT (there was a huge scandal in the UK a few years back and WH Smith for one, got a load of stick off one of the broadsheets) and he stomped off in a huff.
The next guy in front of me was also taking his time because he had all his ticket and passport details on his mobile which was proving difficult to scan and when he came to pay for his Coke and bits, he shoved up his credit card. For THB 120 odd? Aye he was an American...
Still, I had time, I saved a bundle on the drinks and were we glad to have them on the plane as Euro Wings were charging a flat rate of 2.50€ for any liquid refreshment. Ouch.