If you dont mind a small hotel, I can heartily recommend this little gem on the west coast of Koh Samui, called Rajapruek Resort. Right ON the beach, it gives you fabulous sunset-views on a relatively quiet stretch, unlike the horrors on the east coast. However, this has now been spoilt to some extent by something called the Nikki Beach Club, right next door to Rajapruek, which is basically a LOUD beach bar.
The hotel itself is run by two young sisters….and very efficiently at that! Lovely, unpretentious rooms and stand-alone cottages (bungalow 4 is to die for), decent restaurant and bar with good service. And all at an unbelievable price!
Check out the reviews on Tripadvisor….