The five-star hotel Le Meridien Phuket owns the land in front of the beach, and during the daytime, they only allow access to hotel guests. However, if you do not want to stay at the hotel, you can still access the beach if you arrive by sea. All the beaches in Thailand are public; thus, the hotel does not own the beach itself, only the land in front of the beach.
Read more in the article Relax Beach.