I was at Thai Angel recently and was told by the friendly staff that Thai Chef was there so it would be a good night if one is looking for Thai authenticity.
Thai Angel is 141 Grand Street.
For those looking for authenticity that goes to the heart of Thai cooking, a Thai natinal living in NYC told me to go to Amherst in Queens or Woodside around 60th to 64th Street.
For those confined to Manhattan, I recommend Thai Angel when the Thai chef is there, which I think is most nights.
The atmosphere is good, and I recommend ordering from the "Original Thai" portion of the menu, which consists of dishes most Thai people know from eating meals cooked at home. You can talk to the Thai wait staff for insights on how to order the more authenitic dishes.
A 12 ounce bottle of delicious Chang Beer is only 2 dollars at Thai Angel.
141 Grand St, New York, NY 10013