Ko Muk

Ko Muk (Koh Mook) is an island off the Trang coast in southern Thailand, part of the Trang island group in the Andaman Sea. It is best known for a sea cave that leads to a hidden inner lagoon and beach, and for a mix of small sandy bays and fishing-village accommodations.

The most famous feature is the sea-cave passage that connects the open sea to an internal lagoon and small sandy beach; visitors arrive by longtail boat and enter the cave at low tide to reach the sheltered bay. Other attractions include snorkeling along nearby reefs and low-key village beaches with guesthouses and eateries.

The island has long been home to local fishing communities and developed modest tourist infrastructure from the late 20th century onwards to serve beachgoers and day-trippers. The sea cave is a natural formation rather than a man-made structure and has been the island’s principal draw for visitors.

Ko Muk lies off the Trang coastline and is typically reached by boat from the Pak Meng area or nearby mainland piers in Trang province. The island is one of several small islands used as bases for snorkeling and short island-hopping trips.

• Tide-dependent access: Access to the sea cave is tide-dependent; the tunnel is passable only at low tide and during calm sea conditions, so plan visits around local tide tables.

What to See#

• Emerald Cave (Tham Morakot): A sea cave known locally as Tham Morakot or the “Emerald Cave” that is reached by a short boat ride and a brief tunnel swim at low tide to an inner lagoon and small sand beach.
• Village and pier: A small coastal village and pier area serving local fishing communities and guesthouses, providing the main arrival point for boats and island services.

• Plan the Emerald Cave (Tham Mor) visit for low tide and go with a local longtail operator - the cave is only passable at certain tide levels and operators time the crossing for you.
• Arrive early or stay overnight on Koh Mook to avoid the busiest day-trip traffic; early mornings mean calmer seas and shorter lines for the cave.
• If you want reef time, coordinate snorkeling stops with your boat operator so you visit sheltered coral areas in the morning when waters are usually clearest.