Koh Samet is a very nice, "wild" island at 3.5h from Bangkok. The road is new and you can discover the wild part of the place with a scooter. Some beaches are really beautiful with few tourist; just avoid the first beaches after the port. But further, in South Samet, the landscape become really wonderful. Quiet clean water, perfect relaxing place. 200 bahts entrance for Foreigners, 40 bahts for Thai or Expats (just show your thai driver license). Enjoy!