Sungai Kolok's food scene is pretty basic, with lots of shopfront noodle and rice joints along with a few Muslim eateries to sort out your roti fix.
Little English is spoken, so if your Thai, Malay and/or Yawi is lacking, now is the time to brush up on your gesturing. There is a cafe on the ground floor of the Thailiang Hotel, which does lunchtime curries, and also serves breakfast. Otherwise on the corner of Charoenkhet Rd, and just before the police station under a covered mini food market there's a half-dozen stalls doing a pretty good range of Thai food.
On Asia 18 Rd, near the Genting Hotel there's a bunch of coffee shops and food stalls, which, while more popular in the evening are also open through the day. The Seesom Restaurant on the corner of the night market road and Charoenkhet Rd does very good Thai food and although they specialise in seafood (try the crab) they do most Thai standards. They also have a comprehensive English language menu.
Lastly, on the road in front of Thai Farmers Bank and at right angles to Charoenkhet Rd there's a lively street eatery at night. There are many stalls with tables and chairs on the road. This is the best place in town for a cheap dinner.