Over the past half-century, Thailand's health profile has been undergoing an epidemiologic transition in association with various fundamental societal changes, shifting from one with a predominant burden of communicable disease to one in which noncommunicable diseases and accidents now predominate. The primary question is why have the disease rates in the Thai population changed? Answering this question requires an examination of the underlying transitions in social and contextual factors. This paper explores, using published data, how housing conditions, as one set of environmental health risks, have undergone transition in recent years and how this change maps on the health-transition process. A combination of economic development, urbanization, modernization, and increased health literacy resulted in a range of health-protecting changes in housing design and materials. Pre-eminent among such changes are improvements in household sanitation and in equipment, ventilation, and fuel pertaining to indoor cooking and heating. In tropical countries like Thailand, gains have been made in mosquito-proofing houses and in minimizing open pools of water to combat the risks of malaria, dengue fever, and other mosquito-borne infections. Meanwhile, the growth in shantytown and slum housing around the urban fringe, often in precarious environmental settings, introduced a negative dimension to the evolving profile of housing-related health risks, whereas the urban sprawl of modern residences creates health risks that are due to traffic crashes and the lack of walking in daily transport.