Chumphon may be a mediocre tourist destination on other fronts, but when it comes to food, they've really got their act together.
You don't really need a travel guide to find good eats--just stop at any of the Thai-Chinese style restaurants along Sala Daeng Rd, or anywhere else in town, and you're bound to stumble on a surprisingly tasty meal. The one on the ground floor of the Sri Tai Fa hotel is particularly good.
Also, there's a great nightly market along Krom Luang Chumphon Rd. An amazing variety of food is on offer from the numerous stalls stretched out along the roadside, and the seafood places along the same street draw nightly crowds with good, cheap food, staying open until the wee hours.