Ko Samui is a fairly big island. The most popular and commercialised beaches are Chaweng and Lamai, while the northern beaches and their adjacent villages of Mae Nam, Bophut, Bang Rak (Big Buddha) and Choeng Mon are more peaceful choices, and the west coast beaches are still (comparatively) quiet. Update: Bophut and Choeng Mon are not much good for swimming because of murky seawater. Chaweng and Lamai have much clearer seawater, so better for swimming