The short version
Thon Buri is a broad west bank district where old canals, railway land, markets and newer towers share an uneven urban fabric. It is less curated than the riverside developments across the water, and often more rewarding for someone who wants local Bangkok rather than a finished lifestyle district.
The practical split
Wongwian Yai and Talat Phlu are the most useful urban pockets, with rail, food and a strong sense of place. Roads towards the canals and southern edges become more dependent on buses, motorbike taxis and private vehicles. The river is near, but bridges and traffic mean that “across from the centre” is not a reliable commute description.
Getting around
The BTS Silom Line serves Wongwian Yai and the southern west bank, while commuter rail and buses fill the gaps. Thon Buri’s internal journeys are the issue: rail gets you along a corridor, not necessarily to the door. Choose the station before choosing the apartment.
My verdict
Thon Buri is a good fit for residents who like markets, temples and an unvarnished neighbourhood life. It asks more of you than central Sukhumvit, especially if work is on the other side of the river. I would choose Talat Phlu or Wongwian Yai for access, then accept the city noise that comes with it.