Past the Marine Science Research Station and Aquarium (a let down by Bangkok standards, but good for the kids) to the southeast side of the island sits the Chudhadhuj Rajthan Palace Museum and grounds.
When France sent troops to blockade the Gulf of Thailand and occupy Ko Si Chang in 1893, construction of the palace ceased. Since 1978, Chulalongkorn University, with the financial backing of the Thai government, has assumed responsibility for the caring and preservation of the remaining structures.
The grounds house 12 main attractions, and have an abundance of English-Thai signage so you'll never lose your bearings. The three mansions â€“ Vadhana, Phongsri, and Abhirom â€“ are quaint given their titles, but for antiquarians they are architectural marvels, their insides converted into modest gallery spaces.
Phongsri Mansion (Ruen Phongsri) is worth a visit for its fascinating shape and unlikely European sculptures. The Wooden House by the Sea (Ruen Mai Rim Talay), a delightful green house that is rumoured to have been a place of rest for Westerners linked to the royal family, has a coffee shop with outdoor seating for intimate chats and a mangosteen sherbet, exhibitions on the history of Ko Si Chang, and white windows that open out to the sea.
The Chedi-top Ordination Hall of Asdankhanimit Temple (Phra Chedi of Wat Asdankhanimit) might be the most unexpected gem on the island â€“ a gothic-style consecrated hall with stained glass, an arched roof, and a marble floor. The grounds also serve as a sublime spot for a picnic by the shore, and are peppered with fountains and benches to enjoy the surrounds.