Mu Ko Chumphon National Park protects a wide sweep of coast, islands, reefs, beaches, mangroves, creeks, and forested hills near Chumphon. The visitor centre is modern and useful, and the easiest outing is the boardwalk through the mangroves and over the tidal creeks.
Ask locally about current trails and boat options, because the park is large and conditions vary by season. Even if you only have a short stay in Chumphon, the mangrove walk gives a quick sense of the coast beyond the town.