I love Thai Bistro :o) I work in Medford and we eat here for lunch regularly. For the most part, you can simply pick a dish from the menu and ask to have it made vegan style and they will alter the recipe (if needed) to be veg friendly.
The restaurant is clean, the staff is friendly and helpful. I have eaten here many times and never had a bad experience. The food is always fresh and made when you order it.
They also have a very good buffet, but the veg options are not well marked and you will have to ask about the dishes. However, when I have done this, the staff is really great about finding out for me (even going into the kitchen to ask the chef what is in the dish if they don't know).Pros: Clean, pleasant atmosphere, Friendly staff, Fresh food
Cons: Can be slow if busy