Is Railay Beach worth visiting?

Yes. Railay is one of those places that looks exactly like the photos and then exceeds them once you're standing there, mainly because no photograph properly conveys the scale of the limestone cliffs. Phra Nang Cave Beach at the southern end of the peninsula is one of the better beaches in Thailand: small, sheltered, clear water, and cliffs that rise directly from the sand rather than framing it from the back.

The fact that you can only reach Railay by longtail boat (limestone cliffs cut it off from any road) is both the inconvenience and the reason it's worth visiting. That access barrier keeps it from becoming fully overrun. It gets busy during the day (the 4 Islands tours stop at Phra Nang), but it calms down significantly by late afternoon.

The version that isn't worth it

Arriving by speedboat tour at 11am when the beach is at its most crowded, spending an hour there, and leaving. That version of Railay is fine, but it's not the reason to go.

The version that is worth it: taking the first longtail from Ao Nang in the morning, walking straight to Phra Nang before the tours arrive, and spending a full day there. Or staying overnight so you have the beach at 7am to yourself.

Worth it even in the shoulder season?

In the wet season (May to October) the sea gets rougher, the water can cloud up, and some boat services are suspended on bad days. Railay is still accessible when the water is calm, but it's less reliable and noticeably different from the dry-season version. If you're visiting between November and April, don't skip it.

For getting there and what to do once you arrive, see the Railay Beach guide.