My favorite Thai place in town...I haven't been to all of them yet, but I've been to A LOT! I order the Rad Prik fish (either the Pompano or the Red Snapper) quite often because they are amazing! I've also ordered the grilled squid too many times to count, it's amazing, and very fairly priced--it comes with 2 whole squid. The green sauce that comes with the squid is what makes it special... be careful tho, it's a bit spicy!
The staff is always friendly and attentive. After certain hours they have a couple guys singing and playing instruments, very mellow and sounds really good! I always end up leaving them a tip!
I would say it's a lot better than Lotus of Siam. I've eaten there a couple times and left mildly disappointed each time. Weera Thai would be my close second favorite. Hope this helps you! I highly recommend Khun Chai!