We found this place by turning down Suan Phlu 8 and looking carefully on the right side of the street for the red-and-yellow triangular Jay (sect in Thailand whose diet is similar to vegan) flags. We also asked a few people on the street by showing them the "I eat Jay" card we got written in Thai (which has proved helpful several times, I recommend it), and they pointed us in the right direction.
There seems to be no language other than Thai spoken or written here, so hopefully you find entertainment in gesturing and pointing to order! The food was all Jay/vegan as far as we could tell, and pretty standard Thai fare. Although there were pictures of some sandwiches on the walls, they had just basics out for weekday lunch when we went -- fried rice, a curry or two, fried noodles, mock meat in salty sauce.
We paid 40 baht each for a plate of food and complimentary ice water, so quite cheap. Overall, the food wasn't too special but if you're looking for 100% vegan and nearby, check it out.
Cons: Can only point to order, No restaurant service or atmosphere