From Malaysia Factbook
The Burney Treaty was a treaty signed between Siam and the British in 1826. Named after Henry Burney, the head emissary from the East India Company, it resulted from Siamese intention to attack Perak and Selangor after the Siamese successfully invaded Kedah. The British knew that this would disrupt trade and so they initiated the treaty with Siam. Under the treaty, the British acknowledged Siamese claim over the four northern Malay states of Kedah, Kelantan, Perlis, and Terengganu. The treaty further guaranteed British ownership of Penang and their rights to trade in Kelantan and Terengganu without the Siamese interference. The four Malay states were not represented in the treaty negotiation.
2. In 1909, the parties of the Burney Agreement signed a new treaty in Bangkok that superseded the 1826 treaty. Known as Bangkok Treaty, the Anglo-Siamese Treaty of 1909 transferred the four Malay states from Siamese to British dominion.