Found a fantastic vegan/vegetarian restaurant on happycow.net
Called pooh's kitchen
12 Pooh's Kitchen
Soi Green Peace Haad Rin, Koh Phangan
Distance: 5.3 mi.
A small outdoor restaurant in Haad Rin at the end of lane where Green Peace restaurant is. It is run by 2 ladies who are passionate about healthy eating. Will make food to your specifications no worries at all