Currently approximately 9 million tons of plastic enter the world's oceans annually. This is a major transboundary problem on a global scale that threatens marine wildlife, coastal ecologies, human health and livelihoods. Our concern in this paper is with the environmental governance of marine plastic pollution that emanates from Thailand, the sixth biggest contributor globally. By zooming in on land‐based polluters in Thailand, we highlight both the systemic nature of the marine plastic problem and the relative impunity with which drivers of transboundary environmental harm function at all levels of governance. Drawing from 19 interviews conducted with actors from the public, private and non‐profit sectors, we examine three stages of the problem: production, consumption and waste management. We found that three major barriers prevent Thailand's government, private sector and citizens from engaging in the sort collective action needed to reduce marine plastic pollution. They are: (i) insufficient incentives to enact political change; (ii) scalar disconnects in waste management; and (iii) inadequate public and private sector ownership over plastic waste reduction. As the state alone cannot change corporate and consumer behaviour, we argue that multi‐stakeholder efforts across organisational scales of governance and administrative boundaries are needed to address the barriers.

In the wake of the costly 2011 floods, the city of Bangkok struggled to respond to the water inundating Thailand’s major hub. In response, Thai leaders primarily blamed the external forces of natur...