Tonsai Beach is the lesser known beach of Railay peninsula. At a length of around 600 metres, it runs on from Railay West, separated by a rock face at high tide, and faces south. Stuck between two high limestone cliffs, it can be reached by foot from Railay West at low tide. Quieter than the other beaches, Tonsai Beach hosts a few hotels with names like Dream Valley Resort, Tonsai Bay Resort or Mountain View Resort, as well as some beach restaurants and bars, that makes it really the perfect place to get away from it all.

The beach of Tonsai is not renowned to provide vacationers with great swimming or snorkelling: reefs and rocks right in front of the sand make it dangerous; at low tide, it is almost impossible to beach at Tonsai, even for long-tail boats. A legend says that in the eighties, the beach was owned by an Australian citizen who tried to sell it to Club Med; when the Club Med people came, it was low tide and their long-tail boat could not reach the shore. The Australian then decided to dig a channel with dynamite in a way to make the beach accessible whatever the tide level. Unfortunately, after months of efforts, the channel was still not large enough to be usable, so he gave up. This means the rugged and more untouched vibe around Tonsai remains even today.