In the year of 1376, the King Uthong also known as Ramathibodi I, founded the city of Ayutthaya, อาณาจักรอยุธยา as the capital of his Kingdom and occupied the Sukhothai, สุโขทัย Kingdom approximately 640 km to the North of the country. The Ayutthaya, อาณาจักรอยุธยา Kingdom during the period of over the four hundred centuries expanded to become the nation of Siam whose borders were roughly similar to those of the modern Thailand today. Excluding the areas of North of Siam whom the Kingdom of Lanna Thai, ล้านนา were in power and control.
King Uthong declared the royal name of Ramathibodi I in 1351. The Siamese state based at Ayutthaya, อาณาจักรอยุธยา in the valley of the Chao Phraya River, แม่น้ำเจ้าพระยา grew from the earlier Kingdom of Lavo, known as the Lopburi, ลพบุรี Province today. The Sukhothai, สุโขทัย Kingdom was then absorbed by the growing Lavo, ลพบุรี and Subharnaburi Kingdoms and the Kingdom of Sukhothai, สุโขทัย. In 1351, King Uthong moved his Kingdoms base to the South of Siam near the river of the Chao Phraya, แม่น้ำเจ้าพระยา to escape the threat in case of an outbreak or attack. On an island in the river of which is the seaport city of Ayutthaya was settled before and King Uthong founded a new capital which he called Ayutthaya, อาณาจักรอยุธยา named after the Hindu holy city Ayodhya in the northern area of India. Ayodhya is the birth city of the Hindu god Rama who is the hero in the Hindu epic Ramayana.