Rama III

Phra Bat Somdet Phra Nangklao Chaoyuhua (Thai: พระบาทสมเด็จพระนั่งเกล้าเจ้าอยู่หัว, RTGS: Phra Bat Somdet Phra Nangklao Chao Yu Hua; 31 March 1788 – 2 April 1851), personal name Thap (Thai: ทับ), also styled Rama III, was the third king of Siam under the House of Chakri, ruling from 21 July 1824 to 2 April 1851.

Nangklao was the eldest surviving son of King Rama II. His mother Sri Sulalai was one of Rama II's secondary wives. Nangklao was likely designated as heir by his father. His accession was uncontested and smoothly confirmed by the grand council. Foreign observers, however, falsely perceived him as having usurped the prior claim of his younger half-brother Prince Mongkut, who was born to Queen Sri Suriyendra and thus "legitimate" according to Western customs. Under the old concept of Thai monarchy, however, a proper king must emulate Maha Sammata in that he must be "elected by the people." Ironically, Mongkut may have later contributed to this misconception, when he feared that his own accession might be perceived by foreign observers as a usurpation.

During Nangklao's reign, the military hegemony of Siam was established by putting down the Laotian Rebellion (1826–1828, in what would come to be called Isan), the Siamese–Vietnamese War (1831–34), and the Siamese-Vietnamese War fought in Cambodia (1841–45).