Joseph Huddart in 1801 included these directions for navigating the islands, "To the N.W. by N are two islands of about the same height as Poolo Carnom [Ko Samui]; the first, called SANCORY [Ko Pha Ngan], is 7 leagues from Carnom; the other...,named BARDA, or Bardia [Ko Tao], is 7½ leagues from Sancory. (A league is approximately 3 nautical miles or 5.5 km.)
On June 18, 1899, King Chulalongkorn visited Ko Tao and left as evidence his monogram on a huge boulder at Jor Por Ror Bay next to Sairee Beach. This place is still worshipped today
In 1933 the island started to be used as a political prison. In 1947 Khuang Abhaiwongse, prime minister at that time, pleaded and received a royal pardon for all prisoners on the island. Everybody was taken to the shore of Surat Thani and Ko Tao was abandoned again.
In the same year Khun Uaem and his brother Khun Oh reached Ko Tao from the neighbouring Ko Pha Ngan by trying out their traditional sail boat, for that time a quite long and dangerous journey. Even though the island was still under royal patronage, it did not stop these pioneers claiming themselves a good part of the land on today's Sairee Beach. Having brought their families over, they began to cultivate the excellent soil, forming the first generation of the present-day community. They lived a simple and tough life harvesting coconuts, fishing, and growing vegetables, which were also traded with Ko Pha Ngan. Despite the difficulties in reaching the island, the population grew steadily.
In the 1980s overseas travellers began to visit Ko Tao and quickly became a popular destination. As a consequence, bigger, faster and safer boats were used to allow easier access to Ko Tao. In the 1990s the island became known as a diving site.