Zijian D.
Yelp
As far as I can tell, this is the only Thai restaurant in San Juan. It's also the best. As a compliment, I'd say that even if it weren't the only one of its kind, it'd still be the best! The service is very quick and friendly here.
I enjoyed my gin and tonic. They have a decent selection of gins and an interesting cocktail menu. It seems they put a lot of effort into their cocktails as well as their food.
As for the food, we ordered the Pad Thai, papaya salad, and green curry, all level 5 spicy. If PR makes you miss spice, this is the antidote. The heat level was nice! Everything was just well-prepared and tasty. The green curry came with a big bowl of white rice, and the papaya salad came with some tasty sticky rice. The Pad Thai wasn't too sweet, and the chicken wasn't overcooked. I probably would recommend getting chicken with the green curry, though - we ordered beef with it, but it wasn't quite as nicely cooked as the chicken with the Pad Thai.
This place is pretty popular, and with 50% capacity, you'll either need to come early or make a reservation a day or more in advance to secure your table. The restaurant is a short walk to La Plaza del Mercado Santurce (La Placita), and there's paid parking ($8 till 11PM) across the street. The on-street parking within walking distance seems to fill up quickly, so unless you get here quite early, you may end up having to pay to park, since there's no dedicated parking for the restaurant.
Enjoy! :)