Burney Treaty 1826 - The treaty acknowledged Siamese claims over the five northern Malay states of Kedah, Kelantan, Perlis, Terengganu—the future Unfederated Malay States—and Patani.
The treaty further guaranteed British possession of Penang and their rights to trade in Kelantan and Terengganu without Siamese interference.

Anglo-Siamese Treaty of 1909 - Thailand relinquished its claims to sovereignty over Kedah ,Kelantan , Perlis and Terengganu

Article 1
The Siamese government transfers to the British government all rights of suzerainty, protection, administration and control whatsoever which they possess over the states of Kelantan, Tringganu, Kedah, Perlis, and adjacent islands. The frontiers of these territories are defined by the boundary protocol annexed hereto.
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how lah this topkek fella can become professor?