The Siamese revolution of 1932 or Siamese coup d'état of 1932 (การปฏิวัติสยาม พ.ศ. 2475 or การเปลี่ยนแปลงการปกครองสยาม พ.ศ. 2475) was a coup d'état by Khana Ratsadon (the People's Party) which occurred in Siam on 24 June 1932. It ended Siam's centuries-long absolute monarchy rule under the Chakri dynasty, and resulted in a bloodless transition of Siam into a constitutional monarchy, the introduction of democracy and the first constitution, and the creation of the National Assembly. Dissatisfaction caused by the economic crisis, the lack of a competent government and the rise of western-educated commoners fueled the revolution.
King Prajadhipok remained on the throne and compromised with Khana Ratsadon. Two coups occurred a year later, in April and June amid infighting within the government over Pridi Banomyong's socialist economic plan and a rebellion of the royalists.
Since 1782, the Kingdom of Siam had been ruled by the Chakri dynasty. After 1868, King Chulalongkorn (Rama V) reformed a medieval kingdom into a centralizing state of absolute monarchy. The monarchy started to make royal and nobility hierarchy, the Sakdina, to be the most critical aspect of Siam political system. Towards 1880, Chulalongkorn asked of Europe an initiation into modern culture and showed a decided preference for England's Anglo-Saxons culture. In 1910s, King Vajiravudh (Rama VI) sought to legitimise absolutism through Thai nationalism, using Western approach, by appointing more able commoners to the government. A commoner involvement disappointed the aristocracy and nobility. Rama VI carried out unpopular policies that lowered the influence of the royal family.
During the reign of King Rama VI, the government’s fiscal health was eroded. Lavish spending on the court, inability to control the corruption of the King's inner circle, and his creation of the Wild Tiger Corps to promote modern-style nationalism were widely deemed as wasteful. By 1920, fiscal mismanagement and the global economic downturn took the state budget into deficit.