I visited Ko Samet a while ago and here is the latest tips if you are looking for sex in Ko Samet.
There are lots of possibilities to hook up with the tourist girls. Lots of horny young girls from Sweden and many other countries come to party to this island.
You can find sex workers with the apps like WeChat from the island and also from the clubs near Samed Pavillion Resort.
Ko Samet is not very good for mongering, but if you are young and goof looking you should get laid quite easily.
There are also many massage parlors in the main street where you can also find 7/11 shop and restaurants.