The southern dialect is spoken the fastest, and the locals like to shorten words to single syllables, and shorten sentences to one or two words. Formal education is poor in this area, and it shows in the way they speak. Since the south has quite a bit of island tourism, quite a lot of Thais from Bangkok move to this region to make money. As such, you’ll meet a lot of people that speak the central dialect. The dialect of the south is called Southern Thai, or ภาษาไต้. Just as a side note, if you go really really deep south, you’ll find a population of Muslims that speak yet another dialect that isn’t based on Thai.