Aside from tiny food stalls in Ta Pai Yoe village, which look no different than the private kitchen in someone's house, there were at time of writing no free standing restaurants on Ko Phra Thong (that we could find anyway). Luckily, the resorts all do a good job of satisfying hungry travellers.
For a home cooked, authentic Thai meal, Mr. Chuoi's is a good place to start. Frequented by locals as well as travellers, Mr. Chuoi offers a small hand written menu with all items running between 80 and 120B. There's nothing small about the portions — we tried a chicken massaman curry and a green curry, both of which were not only delicious and hearty but also served in what seemed like bottomless bowls — each was easily large enough for two to share. Mr. Chuoi's also offers some delicious fried bananas and is probably the island's liveliest spot to kick back with a beer or cocktail (they also have a limited bar) and chat it up with fellow travellers and divers. We didn't make it to the restaurant at nearby Seaview, but a few people staying there had good things to report. Both Chuoi's and Seaview also offer basic Western style breakfasts.
Over at scenic Phra Thong Bay, Horizon Bar nails the beach bum bar atmosphere while offering some decent food as well. The green curry we tried here wasn't quite as flavourful as at Mr. Chuoi's, but it was 40B cheaper and certainly not flavourless. Horizon also offers perhaps the best place on the island to enjoy dinner and drinks while watching a heavy red sun sink below, well, the horizon.
If looking for something with a little more flash, head over to the restaurant at Golden Buddha Resort. This is also a good sunset spot and easily the most romantic dining setting on Phra Thong. The food is good too — on the evening we visited they were offering a set dinner menu of Luffa soup, chicken with Indian curry, fried fish, roast pork ribs with sesame sauce, and fresh fruit, all for 545B per person. Golden Buddha also serves up french toast and eggs for breakfast, and simple, authentic Thai dishes for lunch.
They also have the island's most extensive bar and are able to make cocktails like mojitos and margaritas. While drinks and fruit are available any time, breakfast runs only from 7:30 to 10:30, lunch from 12:30 to 14:30, and dinner between 7:30 and 8:30, although for dinner it's possible to reserve a later seating time in advance.