Living a bit outside the city doesn't mean you have to go without all the nice things downtown has to offer. We do have shoppings malls here in the south, and we have delicious vegan restaurant. I haven't actually seen a local (Thai) vegetarian restaurant, most of them go all the way down to vegan food.
That means no milk, no fish sauce, no eggs. Even if it looks like, it is not (the Italian Govinda vegetarian restaurant for example has milk products like cheese).
Srinakarin road (right next to the SCB bank). It is open from 6am in the morning until late afternoon every day except Sunday (I haven't see it open in the evening, but that might be because I am usually not in this area at that time). What you get there is everything the Thai cuisine has to offer. They have a Thai style buffet, where you choose the dishes you want. It changes every day. They usually offer Nam Ya, a spicy coconut soup that is served with pickles and vermicelli, and they even have Thai Noodles with soy protein balls as soup or dry.
Per dish you pay about 30-35 baht, you can eat there or take it home. The restaurant also offers a wide range of vegan products, from Palo mushrooms to mock meat like chicken wings and duck breast and soy protein pallets.
Parking there is a bit tricky, there is a SCB bank next to it that has some parking space or you just drive into the small Soi there. I haven't figured out the name of the restaurant yet, maybe you can read it from the banner outside in the picture and let me know (I have some problems reading non-traditional Thai fonts)
Not far from the Srinakarin/Soi Wat Dan Samrong intersection (before Foodland on the left when you come from South) is another vegan place: This one is selling Japanese vegan food. Yes, I am talking about Sushi galore without any Tuna being harmed. No idea how the do it, but it looks good and it tastes good.
Expect limited English skills, but the menu is in English and we never had a problem with the order. It is not that much crowded, but seem to have a decent followership to survive there.
Other vegan restaurants are Govinda in Sukhumvit 22 (100 meter on the right), and there is also another more fancy vegetarian places right next to it. The food court at the 5th floor at Terminal 21 has a vegetarian stall and so does the food court at Central World (7th floor, walk through the supermarket, the vegetarian booth is on the left). Seri Market at Paradise Park also has one vegetarian stall.
Do you know any more vegetarian or vegan places? Please let me know.
(By the way I am neither vegan nor vegetarian. I just don't like to eat meat too much and vegetarian food is usually cheaper.)