Short answers, pulled from the story.
The Ayutthaya Kingdom was a Thai kingdom in Southeast Asia that existed from 1351 to 1767, centered on the city of Ayutthaya in Siam, present-day Thailand. It is considered the precursor of modern Thailand.
Ayutthaya fell on the 7th of April 1767, after a 14-month siege, to the Burmese forces of the Konbaung dynasty. The city was completely destroyed, ending the 417-year-old kingdom, and an estimated 200,000 Siamese died during the war.
Ayutthaya was traditionally founded by King Uthong on the 4th of March 1351, though this has long been debated. Chris Baker and Pasuk Phongpaichit record at least seven legends about who Uthong was, and the chronicles preserve almost nothing about him beyond the year of his death.
European travellers in the early 16th century called Ayutthaya one of the three great powers of Asia, alongside Vijayanagara and Ming China. In the 17th and 18th centuries it became a center of international trade and a middleman between the great empires of the early modern world.
The reign of King Narai, from 1657 to 1688, was known for Persian and later European influence, including the 1686 Siamese embassy to the French court of King Louis XIV. Narai leased the ports of Bangkok and Mergui to the French and welcomed French Jesuits, until his commander Phetracha staged a coup in 1688.
Siam recovered quickly, with Phraya Taksin retaking the ruined capital from the Burmese garrison at Pho Sam Thon in June 1767 using his ties to the Chinese community. He established a new capital at Thonburi, and the seat of Siamese authority moved to Thonburi-Bangkok within fifteen years.