When looking for a hotel or resort on Koh Samet you should also consider the beach where you want to stay as there many beaches on Koh Samet. Actually there are about 16 beaches but lets start with the first 2 biggest and most popular.
The northern beaches like "Ao Noi Na" and "Ao Luk Yon" are more popular with Thai tourists but have less nice beach. Actually no beach.
The southern beaches like "Ao Kiu Na Nok", "Ao Kiu Na Noi" and "Au Karang" are smaller beaches and quite far from anything. And not much places to stay or eat, but if that is what you are looking for these beaches are great!
Hat Sai Kaew, the longest beach of the island and the first one you pass coming from Na Dan pier. It is a bit busy but still very crystal clear beach with some up-scale resorts but also cheaper resort. The nice thing here is that there is a bit more entertainment in the evening with restaurant and fire-shows on the beach. Ao Vong Duen, a bit like Hat Sai Kaew but a bit smaller and with better sunset views. But also a bit less entertainment in the evening.
Then following are the smaller beaches like Ao Prao, the only beach on the west coast with one of the best sunset views of the island. A small beach with only a few hotels. Or Ao Phai, actually a extension of Hat Sai Kaew beach but with the cheaper hotels, although I heard that there are being build some new upscale resorts. To the most beaches are direct boats going from Ban Phe.
How to go to Koh Samet? Have a look HERE