Truly vegetarian or vegan Thai recipes are rare in Thailand. Fish sauce and shrimp paste are signature ingredients of much Thai food, they are also present in curry pastes. Thus a dedicated vegetarian generally ends up having to cook for themselves, and nearly always from scratch, which is a time consuming process.
However as the popularity of Thai food grows internationally he market is adapting to service the demand for vegetaran friendly products and itis possible to get both vegetarian curry pastes and and sauces if you look for them. One of our clients steered me to Fruit &Veg where they stock the Blue Elephant Red and Green Curry pastes. I also found reference on the internet to a Maesri Prik Khing brand and if anyone knows how to source more it would be most helpful.
[edit] There is the Yellow Curry paste distributed by Mae Ploy