Short answers, pulled from the story.
King Chulalongkorn, posthumously honoured as King Chulalongkorn the Great and also known as Rama V, was the fifth king of Siam from the Chakri dynasty. He reigned from the 1st of October 1868 until his death on the 23rd of October 1910, a period of 42 years.
Chulalongkorn took a gradual approach to end slavery, deliberately avoiding the violent rupture he associated with the American Civil War. In 1874, he lowered the redemption price of household slaves born in 1867 and guaranteed their freedom at age 21. The Slave Abolition Act of 1905 ended all remaining forms of Siamese slavery.
In 1893, French vice-consul Auguste Pavie demanded all Laotian lands east of the Mekong River. France sent gunboats into the Chao Phraya River, blockaded the Gulf of Siam, and occupied Chantaburi and Trat. Siam ceded Laos to end the crisis, though French troops did not fully withdraw from the occupied coastal territories until 1906.
The monthon system, established in 1897 in consultation with Prince Damrong, reorganized Siam into a hierarchy of province, city, amphoe, tambon, and village overseen by intendants of the Ministry of Interior. It replaced the traditional Mandala network of semi-autonomous city-states with direct central authority, effectively ending the power of local dynasties.
Chulalongkorn traveled to Europe in 1897 as the first Siamese monarch ever to do so, seeking direct recognition from European courts that Siam was a fully independent power. He also studied institutions he wanted to adopt at home, including the English sanitary district system, which he replicated as Thailand's first sukhaphiban in Bangkok that same year.
Chulalongkorn University, founded in 1917 as the first university in Thailand, was named in his honour. King Chulalongkorn Memorial Hospital, operated by the Thai Red Cross Society, is also named after him and is one of Thailand's largest hospitals.