Mu Koh Chumphon National Park (National Park Visitors Centre), towards Hat Sai Ri (take local bus near Post Office). Take the wooden bus to the fairly new and surprisingly modern visitors centre. Walk the boardwalks through the mangrove forests and over creeks.
The actual Mu Koh Chumphon National Park area of Chumphon Province is huge and takes in islands, reefs, beaches, jungle, mountain, creeks, ocean and mangroves.
You can stay overnight. There’s a camping area, and bungalows at the Pong Pang Viewpoint go for 600 baht per night, and accommodate 2 persons—add 100 baht for each extra person. Dorm beds with no bedding for 50 baht. There are also two restaurants. A good place to visit to make the best of your stay in Chumphon. entry: 200 baht.