If you get tired of the beach (is that even possible?) one option is to rent an ATV (not a motorbike) and do some "resort hopping". This will give you some idea of what is available should you decide to return as there is a very broad range of resort accommodation available on Koh Samet.

This will also give you the opportunity to enjoy some splendid views, especially at the southern tip of the island. 

Be advised though that the roads are very bad (especially at the southern end).

But if you are into exploring and sightseeing and riding an ATV on rough roads the trip can be a lot of fun.