Is there a recommended day trip to the Similan Islands from Khao Lak?

A Similan Islands day trip normally leaves very early from the Khao Lak area and travels via Thap Lamu. The islands are seasonal, and sea conditions, national-park opening dates and weather cancellations must be checked before booking. Choose a licensed operator that explains boat type, group size, insurance, meals, snorkelling supervision and cancellation terms. The trip can be long and bumpy, so consider age, mobility and seasickness. Never accept guarantees of perfect visibility or wildlife sightings. Keep the answer as guidance and verify the final details for your actual travel date.