Although Sri Siam (Vanowen and Coldwater Canyon) has had some solidly good praise on this board, I wanted to post another 'reminder' message. This small place really aims to please its Thai clientele and does not American-ize its food - at least, it doesn't do it too much. We had a conversation with one of the waitresses (in Thai) and she said that they cook "mostly like Thai people cook." We didn't press her on that 'mostly,' but I would guess the reason that it isn't 100% authentic would be availability of some ingredients.
We have gone 2x in the past two weeks and had 6 great dishes out of 6 ordered. Surprisingly good kao yum, a rice salad that comes to the table in need of a good tossing. Add the sauce and toss, ignore the mess you've made of the table and enjoy. This dish has rice, dried shrimp reduced to almost a powder, cabbage, carrots, lemongrass, bai muh groot (dried and shredded kaffir lime leaves, I believe), a sauce made up of what I do not know, a few other veggies and green apples. I suspect that the apples would be replaced with green mango or green papaya in Thailand. Whatever - delicious, if basic. Not a spicy dish, not a sour one - like Goldilocks would say, "this one is just right."
We also had a very simple Thai basil stir-fry with fried tofu that had my girlfriend transported back to Thailand. She kept wondering what exactly what it was that made it taste more 'authentic' than the version of this dish at other good Thai places. We couldn't pinpoint it exactly, but I agree that it was just like off the street in Bangkok. Using bai grapow instead of bai holipa (Italian basil???) certainly makes a big difference.
We have also had a crispy catfish dish, oh lua (transliterated as Oh Lou on the menu) and a killer fried fish cake appertizer. The oh lua tasted quite a lot like a Vietnamese dish - and for all I know, it could be. I never had it in Thailand, although it is a bit like hoy tod (a mussel/egg concoction) only made with shrimp.
No atmosphere to speak of and quite small, but maybe my favorite Thai place in LA proper at the moment.