:In 1351 a man named U Thong founded the city of Ayuthaya (variously Ayudhya, Ayudhaya, Ayutthaya) as his capital city as an island at the junction of Chao Phraya and two other Rivers, not for from Thailand's modern capital, Bangkok. U Thong was probably the son of a Chinese merchant who had married into local nobility; he changed his name to Ramathibodi and set about creating a new center for the Thai world.
In 1378, Ayuthaya defeated Sukothai in battle and became the capital, not just of Ramathibodi's dynasty, but of the entire Thai world. In 1431, the Thai army of Ayuthaya defeated the declining Khmer kingdom of Angkor Wat and sacked Angkor. Ayuthaya was now the leading imperial power of Southeast Asia.
The change from Sukothai to Ayuthaya is important for a couple of reasons. One was the change in the nature of the kingship: The king of Sukothai had been called a Dhammaraja - "Lawful King"; but the king of Ayuthaya was called a Devaraja - God King. Even today the king of Thailand remains a God in the eyes of his subjects.
Second reason was geography: The lowlands surrounding the city flooded annually and was rich in alluvial soil, and the natural positioning made Ayudhaya strategically easy to defend. Being near the Chao Phraya estuary made it accessible by seafaring trading vessels. Thus Ayudhaya became an important foreign trading center. Availability of foreign technology and weaponry also made it immensely powerful among its neighbors.
Ayudhaya's income were from its beautiful products, and from duties levied against foreign trade. Merchants came from China, Java, Malaya, India, Sri Lanka, Persia, Japan, Portugal, France, Holland and England. At its height, Ayudhaya became one of the most important trading centers in the area. Its prosperity may be witnessed from its arts, many aspects of which reached perfection unmatched in Thai history Sukhothai culture.
Ayudhaya fell to an invading Burmese army in 1767 with King Ekathat (1758-67) being the last of a royal line which lasted 417 years. This was the culmination of decades of armed conflict between the two countries. The once glorious city was left devastated and without leadership. Abandoned, it quickly went into ruin. The fall of Ayudhaya was so catastrophic that decades after the event, Thais reminisced about "the glorious old city.