We stayed at Chaweng Beach and only spent time at this beach in Koh Samui, so can't compare to the other beaches. May is considered as a low season, hence we did not feel that the beach was crowded. Many empty sun deck chairs at the beach. Not sure if you can rent it, but they belong to the many hotels and resorts along the white sandy beach. We stayed towards the south of Chaweng beach, and we walked up to the northern part of Chaweng, and found it a better place to swim and play in the sea. The water was crystal clear, and very shallow. You could walk a few hundred metres out and the water was just up to waist level. Many just sit there and feel the small waves rushing in. After some tiring swim and walk, there are plenty of massage huts on the beach, you can also do some shopping as there are many locals selling jeweleries, clothings, bikinis, ice cream etc.
There are also many nice eateries along the beach, and within few minutes of walk, you will reach the centre of Chaweng Street, where you can get anything and everything.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.