Most livelihood research focuses on micro-level decisions affecting occupa-tions but fails to examine wider scale processes that shape markets, institu-tions, and thus livelihood choices. A political ecology framework can helpaddress this gap by providing ways to analyse how multi-scalar and extra-localpractices, policies, and discourses affect local-level socio-environmental out-comes. In the qualitative research reported here, that framework is applied toTha Kam, a peri-urban coastal sub-district of Bangkok, where most residentsare small-scale aquaculture farmers. These farmers have experienced precipi-tous drops in incomes because of two major environmental changes: coastalerosion and wastewater intrusion. The causes are multiple and complex, andmany originate not from practices within Tha Kham but from challenges pre-sent at a larger scale or that start upstream. The political and economic driversof these problems stem from Thailand’s fragmented vertical and horizontalgovernance structure, unequal class relations in which smallholder farmersand peri-urban residents are marginalised, and lack of accountability and rep-resentation. This combination of multi-scalar factors and power imbalanceshas contributed to evolving injustices of peri-urbanisation, all of which are pro-foundly geographical in their significance.