Bandon Bay, on the east coast of peninsular Thailand, has seen rapid development of coastal aquaculture since the 1970s. It has also seen the emergence of conflict between fishermen and aquaculture farmers over competing claims on marine resources. This article examines the roles of state initiatives, environmental changes, and natural disasters in the development of these conflicts. Blood cockle aquaculture was introduced to Bandon Bay through state policies that incentivized in-migration and the establishment of "cooperative communities." After significant damage due to natural disasters in the late 1980s, large-scale government-sponsored rehabilitation projects and an associated influx of capital gave aquaculture a "great leap forward." Environmental changes and government policies triggered adaptations by farmers that led to an expansion of cultivation into new-and illegal-areas, and a transformation of cultivation from small-scale to large-scale farms. The expansion of the aquaculture area brought about conflicts over the use of coastal resources between aquaculture farmers and coastal fishermen. Yet these two communities that had developed from agricultural settlement in the early 1980s had no traditional means of negotiation and bargaining to resolve the conflicts and therefore relied on deep connections to the bureaucratic system rather than relations with each other.