That's the thing: The English don't use the word "conquered". They avoid using it. They believe in some form of parent-child relationship between them and the colonized countries. All commonwealth countries were under the British Empire, but we were not conquered. We were colonised.

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?

btw Sultan Ahmad Tajuddin, Sultan Kedah during that time was in exile @ Penang when it happened. he fleed during the 1821 war and was eventually restored to the Kedah Sultanate in 1842 under Siamese suzerainty

What about what this guy wrote above?