As many cities in the global South are expanding rapidly, their urban form and built environment transforms and thus people's travel demand and behaviour. This paper investigates how the built environment on district level influences individuals' travel behavior and rationales for activity and mode choice in two Bangkok districts. Findings shows that individuals in the sparse outer districtwho belong to larger households and have higher average incomes -travel more frequently, travel much longer distances, use more modes per trip, and rely on private motor vehicles to a much larger extent compared to individuals in the dense inner district. Individuals´ selection of activity location is mainly based on a wish to reach the best facility, disregarding of district, in particular work and education, and to reduce distance, especially for grocery shopping, less so for specific goods and leisure, and least for visit purposes. Mode choice is mainly determined by a combination of time, costs, and convenience. In the absence of high-capacity transit systems Bangkok's motorized vehicle fleet (and use) will most likely continue to grow among its close to 30 fringe and outer area districts located far away from the city centre and work place clusters. Here private motor vehicle use is often the only option. If these residents start driving, land use planning and/or provision of high-capacity transit will most likely have a small influence on how much they drive.