The noodles that i means called Boat Noodles (Thai : ก๋วยเตี๋ยวเรือ).
The Flavor's stronger than nomal noodles. It contains with pork or beef, as well as dark soy sauce pickled bean curd, and some other spices and is normally served with meatballs and pig's liver. If you guys do not eat liver or beef, can tell them that you do not need it.

The cost's also cheaper than others, around 15 - 20 baht per dish.
Location : Easy to find in local place, like street food.