The importance of spontaneous construction raises some questions about the modalities of urban production, especially in developing countries. This thesis presents the case of Bangkok, where the "dense communities," besides the flexibility of their architecture, often crystallize a common site specific history. Rarely taken into account in the metropolis and victims of a negative image, they show, at a local and international level, a stimulating economic and associative dynamism and represent a major challenge in light of the concepts of sustainable development and the right to the city.Through a mainly spatial analysis, interviews and field observations, we approach spontaneous settlements as an incremental construction, result of a process of individual appropriation. We then analyze three configurations or "contexts of emergence" of these constructions: “ancient”, “pure” and "grafted".The first configuration questions the notion of heritage in relation to these popular constructions, dating back to the origins of Bangkok’s urbanization. At the same time, the pure spontaneous housing settlements tend to become real attractive city districts, finely linked to their urban context. With the added spontaneous grafts, which we observed on the social re-housing buildings, informal settlements become a viable way to build the city and a tool for urban development.Spontaneous housing leads progressively to a repositioning of urban actors, the implementation of alternative design processes, renewing the current models of housing production to a shared urban construction.