My knowledge and experience of Thai food is centered around Isan, the northeastern region. It's where my dad lived while he was serving in the army, and also where my Thai family lives (basically my host family in Thailand; their son, my Thai brother, lived with my family for a time as an exchange student when he was in high school and we've been visiting back and forth ever since). Isan food is also popular in other parts of Thailand, and since I'm familiar with it, I tend to order it. Therefore, my knowledge of Thai food from other regions is lacking in comparison.
Our first night in Bangkok, our friend J., who has lived in Thailand for several years now, took us to a southern Thai restaurant around Khao San Road (an experience for another post...) and we ordered something called mataba that turned out to be a kind of stuffed roti served with a bit of pickled cucumber relish on the side:
this description of the dish on Kasma Lola-unchit's site, I'm willing to give it another try when I have the chance.
Note: Also from Kasma Lola-unchit: Apparently "mataba" is the Thai word for what is referred to as "murtabak" in Malaysia and Singapore.