This thesis is a study of the Relations between Siam and Burma during during the primary Reign of King Rama III (1824-1851). Before this period, the two countries were mostly at war but after the English had come to South East Asia, the relations between Siam and Burma underwent a change and the war ended in the Reign of King Rama III. This thesis also deals with the reason why the war between the two countries in the primary Reign of King Rama III ended. The cause of the war between the two countries is also shown. In 1767 B.C., Siam surrendered to Burma. Ayuthya, the capital of Siam was so badly destroyed that it was impossible to be restores. A new capital therefore was founded in Thonburi and later in Bangkok. Howevre, the war actually united Siam. In the Reign of King Rama III the situation changed because the English came in and waged war with Burma. Undecided as to who would win. Siam did not side with England. Thus when victory was on the English side. Siam gained nothing except for the fact it ended the long war between her and Burma. Even though Siam-Burma war was ended. The two countries, still go on spying on each other except ones at Tenasserim Coast that was in the ocupation of England.