we have stayed at Maenam Resort twice for a month each time over the last 2 years.
they do have a lock up facility at reception. i also had no problem with safety completely safe both inside the bungalow and on the beach. i left my swimming paraphernalia on the veranda and even once on the beach one night and it was all there when i went out next morning. the hotel also has a 24 hour security guard as well as CCTV cameras.
Perfectly safe in my opinion.