The treaty between Kingdom of Siam and the United Kingdom of Great Britain and Ireland commonly known as the Burney Treaty was signed at Bangkok on 20 June 1826 by Henry Burney, an agent of British East India Company, for the United Kingdom and King Rama III for Siam. It followed an earlier treaty of 24 February 1826, in which Siam became an ally of Britain against the Kingdom of Ava (Burma), with which Britain was at war. A Siamese army was actually raised and equipped, but took no serious part in the war due to ill-feeling and suspicion arising from the Siamese invasion of Kedah in 1821.
In 1822, John Crawfurd undertook a mission to the court of King Rama II to determine Siam's position on the Malay states. The treaty acknowledged Siamese claims over the four northern Malay states of Kedah, Kelantan, Perlis and Terengganu—the future Unfederated Malay States. The treaty further guaranteed British possession of Penang and their rights to trade in Kelantan and Terengganu without Siamese interference. The four Malay states were not represented in the treaty negotiation. In 1909 the parties of the agreement signed a new treaty that superseded that of 1826 and transferred the four Malay states from Siamese to British control.
As the Burney Treaty did not adequately address commerce, that aspect was elaborated in the Bowring Treaty, signed by King Mongkut (Rama IV) on 18 April 1855, that liberalized trade rules and regulations.