I really like Angrid Thai for quick, tasty food. It's in a the perfect location for the theatres, cinemas, bus station, pre-Thirsty Meeples or post-shopping stops. It's even somewhere that's quite comfortable for eating alone, and there are often other weary travellers doing the same.
My favourite dish is the Mosselman curry, made of lamb, potatoes and peanuts. I can't comment on whether it's authentic but it's very delicious and warming. The salads come with the most amazingly piquant and delicious sauce/dressing. It's sharp and moreish. I suspect it's got rice wine vinegar in, and there's definitely chili in there, but I can't identify all the other elements. It beats Wagamama salads hands down, and is up there with Chiang Mai Kitchen for me.
Decor is plain clean wood, there's endless jasmine tea on tap, there are usually a lot of Asian people eating in there which I take as a stamp of approval, and there's always a crazy promotional video made (I would guess) by the Thai tourist board. The subterranean loos smell a bit damp but that's the only negative.
It's not one for a long slow decadent night out, but highly recommended for good quick, cheap food.