I like Sala Thai Cuisine at the Elements, Kowloon Station, which served authentic Thai food.
The restaurant is good enough that Mcdang, one of the famous Thai food critics, wrote his column in a Thai newspaper introducing this restaurant to Thai people in Bangkok.
For the first timer to Sala Thai, I suggest you order Mcdangs list below. Also, you should order white rice to accompany all dishes below which includes appetizer. This is the way Thai eats.
1. Appetizer: Fish cake (good and taste Thai though a bit on the salty side), Spring roll
2. Noodle: Pad Thai (not very good and you will have to add the condiment to boost the taste, ie chili flake and sugar)
3. Main dish:
3.a Lime Steamed Fish (not quite a steamed dish but more of a hotpot style a nice balanced of sweet and sour with no creamy taste like Thai foods that was catered to westerners taste. It tastes exactly like a good one that is served in Thailand)
3.b Exploded crab (not a Thai dish but a tribute to HK styled typhoon shelter fried crab highly recommend by Mcdang)
4. Dessert: Mango and sticky rice got negative review from Mcdang. The sticky rice wasnt cooked right and the mango was sour though the comment sounds typical of this dessert served at almost all Thai restaurant in Hong Kong
I visited this restaurant last Friday and I included my comment on foods I ordered above (in the blanket). For dessert, I had coconut agar, which was surprisingly good, and had no rancid smell, which is typical of coconut based food/dessert in Hong Kong.
I realized that this restaurant got a very low score on the local foodie website, openrice.com. Nevertheless, my understanding is that the low point was mostly from services, which, I believe, was currently not an issue during my visit last Friday.
For those who insisted the food there wasnt good, I suggest other Thai styled restaurant like Thai Basil at Pacific Place. It tastes good on its own but is beyond me why they called what they served and named the restaurant Thai.