This place seems to be veg for religious reasons - you'll see a lot of Buddhist devotional objects hanging on the walls. There's no English menu and the staff also doesn't speak a lot of English. So, you can try to order by getting some help by other guests (mostly locals) or just have a look in the kitchen, what food is available. When we visited Thien Duyen, there was a small choice of mostly cold served dishes, but we also got a Pho (Vietnamese noodle soup), which was quite delicious. Free tea (cold) is available on every table. Don't expect a fancy place or extravagant cuisine, but you'll leave full for a very reasonable price. Also the staff is friendly. If you go there, note that you have to enter the alley and find the restaurant after 100 m on the right (the restaurant at #308 on the main road isn't what you're looking for).