The significant threat of climate change to sustainable development is most acute in developing countries, which are predicted to experience higher occurrences of wildfires, more extreme storm events, rising sea-level and increasing incidence of devastating floods. In studying climate change adaptation policy in a developing country context, this thesis focuses on Thailand and its attempts to respond to international, national, and local pressures to respond to climate change. As there is little research on the nascent climate change adaptation policies in the country, the thesis makes a significant contribution to identifying, analysing, and understanding the key discourses of such policies at the international, national, and local levels. Specifically, it examines how the different discourses at each level shape initiatives to promote climate adaptation and what the implications of these discourses are for sustainable development and the uniquely Thai notion of the sufficiency economy. The research involved examining key texts, including policy documents, national reports, legislation and press releases, and analysing interviews with key actors on climate change adaptation policies at the international and national levels, as well as a local case study of the USAID-funded Mekong Adaptation and Resilience to Climate Change (ARCC) project in Chiang Rai, Thailand. The findings reveal several discourses at each level, with distinctly different implications for sustainable development and for the fulfilment of the aims of the sufficiency economy. Thailand’s adaptation responses were influenced to a great extent by the country’s desire to balance its international obligations with its local development needs. The ideas that the discourses propagate, and the extent of their dominance vary across different levels, each being shaped by the genre of the texts and the key actors involved in producing and disseminating the discourses. Overall, there were stronger links to sustainable development than sufficiency economy in adaptation policy discourses. By examining the discourses of adaptation policy at different policy levels, the research highlights the similarities and differences in how adaptation is prioritised and adopted at each level, including the role of international agencies in shaping local adaptation responses. The study provides a foundation for further research into the role of climate adaptation and its contribution to sustainable development. It also provides a basis for further analysis into the links between the ideas that underpin the Thai concept of the sufficiency economy and notions of sustainable development, and how they can inform national policy and practice.