Almost all the dishes on the menu here have a veg option and as vegans we found plenty of choice -- papaya salad and veggie/tofu pad thai made without shrimp paste or fish sauce as we requested, coconut cream curries and vegetable-rice dishes that are vegan without any special requests, even desserts based around banana, mango, and coconut. Since it's not a vegetarian or vegan restaurant you have the downside of having to pay attention to what you order, but on Koh Phangan all the veg places we found were heavily western-influenced whereas here the food is authentically asian (and very inexpensive!). If you're looking to try local, seasonal, fresh food celebrating those beautiful fruits and traditional flavors, and you'd like to eat vegetarian or vegan, I recommend Pan Thong. Find it amongst the 10 or so businesses in Thong Nai Pan Yai.
They do have a decent selection of drinks, including beer and cocktails, for such a small restaurant. Additionally, you can get food and drink to take away (picnic on the beach?).
The two downsides are that they have only outdoor seating with no anti-mosquito measures, so be prepared for that, and that it's run by just one person with occasional help, so you can't expect a lot of table-side service. They do currently have a puppy running around which should provide plenty of entertainment, however!Pros: Cheap, Selection of dishes, Authentic
Cons: Only outdoor seating, Casual service