Why go
Thonburi explains why a visitor looking at Bangkok’s river sees more than one capital story. Taksin’s base lay across the Chao Phraya from the later Rattanakosin centre. Thinking in that west-bank to east-bank sequence makes the move from Ayutthaya’s destruction to Bangkok’s founding much easier to follow.
The full story
Ayutthaya’s defeat in 1767 left the old capital ruined and political authority divided among regional leaders. Taksin organised resistance from the southeast, then established Thonburi as a new capital on the west bank of the Chao Phraya. His campaigns brought many of the separated territories back under one centre. The capital was short-lived: in 1782, Rama I founded a new royal city across the river at Rattanakosin. The practical geography is the part to keep in mind while visiting Bangkok. Ayutthaya lies upriver as the earlier capital; Thonburi marks the west-bank transition; Rattanakosin became the east-bank royal core. The sequence explains why historic sites on both sides of Bangkok’s river can belong to the story of the capital without having been built by the same court.