I started going to Thai Lahna a few years back, and it's one of the few Thai restaurants that I keep returning to. The Pad Thai uses thin noodles, which is unique and gives it a very different texture. The pineapple fried rice has some awesome spices and the chunks of pineapple add a subtle sweetness to the whole dish. Their curries are definitely good as well.
The appearance is a bit of a "hole-in-the-wall" but if that bothers you, you can always call in for take-out instead. Service has always been fast and polite for me, but that varies based on who your server is, so I can't make any promises there.
Thai food is awesome for vegetarians, and Thai Lahna does not disappoint in this aspect. It's one of those places where you can have a completely vegetarian meal and only notice that there was no meat after your meal. They are definitely generous with their portions and their pricing is very reasonable.