Thailand's most famous royal complex and temple (Temple of the Emerald Buddha); arrive early to avoid crowds and dress respectfully (opens 8:30–15:30).
Blue Temple known for vivid blue murals; Baan Dam (Black House) is an art complex of dark, thought-provoking architecture — both open typically 8:00–18:00.
Afternoon boat excursion to Hong Island (national park) for kayaking and swimming in the lagoon; tours run through the afternoon returning before sunset.
Full-day liveaboard or speedboat snorkeling to the Similan group — crystal waters and excellent reef snorkeling; operators leave early and return late afternoon.