The land border is based on the 1909 treaty between Thailand, then known as Siam, and the British which started to exert its influence over the northern Malay states of Kedah, Kelantan, Perlis and Terengganu in the early 20th century.The four states had earlier been under Siamese control.he border between Thailand or Siam and the sultanates of the Malay Peninsula (Peninsular Malaysia today) has varied throughout history according to the influence the kingdom over the sultanates.