His mission was to negotiate a free-trade treaty. It took around five months for the Burney Treaty to be drawn up and signed by the Kingdom of siam and the United Kingdom of Great Britain and Ireland
on June 20, 1826. It allowed Siamese and British merchants to trade freely. However , all foreign merchants who entered the Kingdom of Siam were required to observe the laws of the country. The treaty helped expand Siam's international trade, which also earned more revenues from import duties. The manufacture of products for export also stated at this time.