I think all good tips been provided. But I try for one rule; IF there are more locals then farangs in a tourist area you are pretty much in for a treat.
If they did serve bad food they would not have customers. Also the food turnover is high so not much get spoilt or kept.
Worst place to eat is huge restaurants with few customers. Serving reheated food will give you problem.
And don't be shy. If you see someone having interesting food then either ask what it is or order the same. Darn, envious of having a first real thai dish.
I can hardly wait for next week and some hole i