What is the best Thai language school for foreigners in Pattaya?

I am in Samui not Pattaya but here I could not give an answer to your question without a better idea of what your goals in learning are, how much time you want to devote and how far you want to go.

One school here focuses heavily on reading the others much more geared to conversation. One school makes the classes very entertaining and social but does not go beyond about lower intermediate. Another is more rigorous and allows you to go to more advanced levels but requires more work to keep up. Some of the schools are focused on everyday living others a more general vocabulary which may be more useful if you want to work with Thais, understand the news etc.