1/2 Sukhumvit Soi 39, 02-204-1056. Open daily 8am-7pm. Also locations at Chaeng Wattana (02-575-2222), Ekamai (02-381-7691), Kaset (02-941-3204), Petchakasem (02-455-4894) and Prachachuen (02-952-5838).
This is probably the closest thing in Bangkok to a health food store that you might find abroad. There are five branches, where you can buy a large variety of mushrooms, organic veggies, nam prik jay, as well as takeaway ready-to-eat vegetarian food like rad na, spicy rice salad and khanom jeen.