The Early Ayutthaya Period was from the reign of King Ramathibodi I (1353 A.D.) to the reign of King Boromrachathirach II (1447 A.D.)
The Middle Ayutthaya Period was from teh reign of King Borommathailokkanat (1448 A.D.) to the reign of King Narai the Great (1688 A.D.)
The Late Ayutthaya Period was from King Thepracha (1689 A.D.) to King Ekkathat (1767 A.D.)