The built-up areas of Nang Thong and Bang Niang in Khao Lak (see map) have many restaurant options to chose from. In addition to Thai, Italian restaurants seem to predominate. There are also two or three Indian restaurants in the Bang Niang area.
Resort restaurants tend to come and go, so I won't try to list any of them here. However, I will give one suggestion which I think has already been around for a little while: Stempher Cafe on Petchkasem Road in the Nang Thong area. They have good coffee, some fantastically delicious-looking cakes, and a menu of Thai and European food. There's also free wi-fi, which a lot of people seem to use. The cafe is very small, and sometimes fills up at meal times.
Aside from restaurants and a few pubs, there is very little in the way of night life to be found in Khao Lak.