Nearly all of Ko Muk's resorts have their own restaurants, with a growing number of standalone eateries geared towards travellers on different parts of the island. You'll find fresh-off-the-boat seafood and even a decent bakery.
Most of the islanders seem to cook for themselves in their own kitchens, with only a couple of nondescript single-wok eateries with one or two tables geared towards other locals in the villages. A few convenience shops along the cross-island road sell fresh fruit and chips, while a nearby stand offers Thai iced tea and coffee. Otherwise, head for the resorts and traveller-oriented restaurants.
Near Haad Farang, Mayow Thai Kitchen was supposedly the area's first restaurant and it still churns out big and tasty portions of Thai curries and other staples like grapao kai (chicken with chillies, garlic and holy basil). Though you miss out on the sea views, the atmosphere is suited to having a few beers while chatting up the helpful and laid-back owners and other travellers. Starting around 70 baht, prices are very reasonable for what you get.
If you don't mind paying a bit more for a table draped in one of Haad Farang's gorgeous sunsets, head to Ko Yao Viewpoint Restaurant and its wide wooden deck perched over some rocks at the beach's far eastern end. They offer sandwiches and fish and chips, but the extensive Thai menu is the way to go. The tom yum soup with fish and garlic-pepper prawns that we tried were both spicy and flavourful -- even if the MSG left our mouths tingling for a while afterwards.
Moving inland, Hilltop Restaurant is another long-running, standalone spot that will make it spicy if you ask. Their motto is "Cheap cheap but different," which only makes sense after meeting the boisterous owner with a hearty laugh and outgoing personality. She's an excellent chef, too. We tried a nameless seafood stir-fry with lots of mushrooms and holy basil, recommended by the chef, and found it very tasty. The tiny open-air restaurant is also a good spot to meet other travellers, but do bring a torch if coming after dark as it's a good half-km walk back to Haad Farang.
Over on Ao Kham, the newish Sugar's Coffee Shop on the boat-strewn stretch of beach that fronts the east-coast village is a go-to spot for a cup of fresh coffee. The gentle couple in charge also offer a reasonably priced Thai menu that includes whole steamed fish with lime-and-garlic sauce (pla nueng manao) for just 120 baht -- less than half of what you'll pay at Sivalai or Charlie. You'll also find a range of Thai dishes for under 80 baht, and ginger or chilli-garlic stir-fries served on sizzling steel platters for 120 baht.
A stone's throw from Sugar's is De Tara, a small resort that also boasts Muk's most stylish restaurant. They do solid cocktails (though their claim of "best margarita in the world" is a bit much) along with tasty Thai dishes, including some Southern specialties like fresh turmeric soup and pad pong karee, seafood stir-fried with egg and Indian curry powder. If you're on the other side of Ao Kham, Nurse House's tiny seaview restaurant is another great option for seafood, including several spicy Thai-style salads.
A few restaurants in the main village focus specifically on Seafood; while we didn't make it to the largest, Team Restaurant, we did have an excellent meal at Family Seafood. Hailing from Kantang on the mainland, the elderly owners spend half of the year serving big, reasonably priced plates of home-cooked food to travellers. The few simple tables are spread out in front of their house, and they'll bring out the available seafood to let you inspect before ordering.
Offering stunning views to the mainland, Sivalai's massive restaurant comes with a similarly weighty menu that includes a range of international foods like pizza, chicken cordon bleu, T-bone steak, sashimi and tempura. The roast-duck sandwich that we tried wasn't bad, though we would have appreciated something better than standard grocery store white bread. They also do an extensive selection of Thai dishes, including unexpected options like jungle curry (gaeng pa), along with seafood barbecue and Thai-Western fusion like sea bass with mango sauce. Expect to pay 150 baht for sandwiches and Thai dishes, and over 200 for Western fare.
Over on Haad Farang, Charlie Resort has a similarly spacious restaurant that also sets up tables perched right over the sand. They offer a good (though expensive) barbecue with options like corn on the cob and baked potato to accompany the red snapper, tiger prawns, chicken and steaks. While the regular Thai dishes are overpriced and watered down for Western tastes, Charlie serves decent sandwiches and burgers on its own house-baked bread. Ko Muk's only bakery also churns out brownies, cakes and doughnuts that, while not worth writing home about, will satisfy your dough and sugar craving.
While beer is available at most of Ko Muk's restaurants, this is not a party island. Both Charlie and Sivalai serve beer and wine to go with a standard set of cocktails at gouged prices. Just inland from Haad Farang, Ting Tong Bar at Mookie's is probably the best place to meet other travellers over a cold one. They even have fire shows on some nights.