These negotiations continued all through 1908 and resulted in a treaty, signed and ratified in 1909, by which Siam ceded to Great Britain her suzerain rights over the dependencies of Kedah, Kelantan, Trengganu and Perlis, Malay states situated in southern Siam just north of British Malaya, containing in all about a million inhabitants and for the most part flourishing and wealthy, and obtained the practical abolition of British jurisdiction in Siam proper as well as relief from any obligations which, though probably very necessary when they were incurred, had long since become mere useless and vexatious obstacles to progress towards efficient government.
Penang was purchased from Kedah in 1786, and Singapore from the then sultan of Johor in 1819.
By a treaty made between Great Britain and Siam in 1902 the northern Malay states of the peninsula were admitted to lie within the Siamese sphere of influence, but by a treaty of 1909 Siam ceded her suzerain rights over the states of Kelantan, Trengganu, Kedah and Perlis to Britain.
Penang was founded on the 17th of July 1786, having been ceded to the East India Company by the Sultan of Kedah in 1785 by an agreement with Captain Light, for an annuity of $10,000 for eight years.
Pulo Penang, an island belonging to the Siamese dependency of Kedah, was granted on a permanent lease to the East India Company in 1786, and treaties were entered into by the sultan of Kedah with the company.