Hiya
Take a look at
www.hotelthailand.com and select Rayong province. It has several choices of hotels on the island and is offering a good package that includes transfers between the pier and the hotel, breakfast, lunch, dinner and boat trip excursion. Go straight to the offer at
www.hotelthailand.com/kohsamet/samedcliff/package.html I don’t know how good the excursion is, but it looks interesting. The same package is also available from asiatravel.com but incredibly expensive because it includes transfers to/from Bangkok by a private car, take a look at
www.asiatravel.com/thailand/prepaidhotels/rayong.html Obviously, you can travel from Bangkok to the pier comfortably by public bus with air-conditioner from the eastern station (Skytrain - Ekamai Station) in Bangkok. The bus fare costs just about $10.
My last visit to this island was about 9 years ago. I stayed at the Malibu resort on Wong Duan beach ( bookable from hotelthailand.com). The beach was really nice and clean and had an excellent view of the sun set. Don’t know what it looks like now. Seem to remember there were minibus services to/from this beach and Sai Kaew beach too. Sorry for the rusty info.
I am very interested to hear what you think after you have returned. I am going to be around in Thailand in February and may revisit the island.