Koh Si Chang
For centuries Koh Si Chang was considered a gateway to Thailand, the spot where huge sailing ships docked and smaller barges loaded goods bound for Bangkok and Ayutthaya. This is still a hardworking port, which means rubbish from the shipping and fishing industries creates a bit of an eyesore. But it's a clean island otherwise.
Koh Si Chang has been a popular retreat for three generations of royalty. In the 19th century King Rama IV noticed that people on this island lived longer than most Thais (to 70 and 80 years). He concluded that this phenomenon had something to do with the island's climate and he started to spend time here. His son, King Rama V, went one step further and built a summer palace on the island, and King Rama VI would spend up to eight or nine months a year here.