Captain Henry Burney, an agent of British East India Company appointed in 1825 as political emissary to Siam, finally meets with success when he concludes an Anglo-Thai treaty of friendship and commerce.

The treaty between Kingdom of Siam and the United Kingdom of Great Britain and Ireland commonly known as the Burney Treaty is signed at Bangkok on June 20, 1826 by Burney for the United Kingdom and King Rama III for Siam.

It follows an earlier treaty of February 24, 1826, in which Siam had become an ally of Britain against the Kingdom of Ava (Burma), with which Britain is at war.

A Siamese army had actually been raised and equipped, but had taken 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 had undertaken a mission to the court of King Rama II to determine Siam's position on the Malay states.

The treaty acknowledges 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 are not represented in the treaty negotiation.