The problem of biodiversity loss has been raised as a significant global issue for several years. There have been many significant attempts to cooperate at an international level. The Convention on Biological Diversity (CBD) was launched as a mechanism for multinational cooperation for global biodiversity conservation at international policy level among the signatory parties. Despite the formulation of the CBD, biodiversity policy has suffered in its framework, institution and practices. Biodiversity has continued being destroyed at a rapid rate. Previous research on biodiversity policy evaluation studied only some parts of the policy cycle but did not point out the strengths and weaknesses clearly leading to difficulties in holistic policy cycle of both formulation and implementation. This thesis evaluates effectiveness of biodiversity policy in Thailand as a signatory nation of CBD, principally in Indo-Burma and Sundaland biodiversity hotspots. They are important as a reservoir of the richest but most threatened plants and animals. While biosphere reserve has been established to allow locals utilising biodiversity as well as conservation, biodiversity threats have continuously been found. The policy was formulated and implemented to conserve them. The research was conducted to address this gap by thoroughly investigating the policy cycle in the development, implementation and evaluation of biodiversity policy, which truly reflecting political, socio-economic, cultural and environmental contexts. Thailand was taken as a case study and within this, three culturally diverse geographic locations were selected: North, Northeast and South biosphere reserves reflecting different ecosystems and cultures. This offered a detailed and complex analysis of development and implementation of the biodiversity policy throughout Thailand. An inductive approach and qualitative methods were applied using in-depth semi-structured and unstructured interviews with policy makers, decision makers, as well as focus groups with local stakeholders through the application of culturally sensitive policy evaluation methods. The findings suggested that biodiversity policy implementation failed in Thailand and policy formulation had a low level of participation from the locals. Local stakeholders demonstrated little engagement with the need for biodiversity information from the government. Bureaucrats, decision makers and policy developers also shared little enthusiasm for initiating effective policy. It is important that awareness raising and education enhancement, particularly with children so that they will learn from early age. At local level, the policy must be carefully implemented to engage local stakeholders in biodiversity conservation. It is significant that biodiversity policy will be effective if it applies a bottom-up approach and requires grassroots participation. The recommendations for biodiversity policy, in the long term, the government should take into account local views towards national policy and bring this to the international level to achieve sustainable biodiversity conservation. Thus, it offers new insights into the success or failure of biodiversity policy in developing countries that was affected by cultural factors which must be taken into account during the entire policy cycle by the international community.