The purpose of this study is to analyze the policy making process of ethanol in Thailand and its determinants whether they lead to a success or failure of policy. The research includes a comparative study of Brazilian ethanol policy which uses ethanol as fuel over 50 percent of total gasoline. Brazil has reduced the reliance on foreign money; moreover, it becomes a ethanol exporting leader in the world. However, the ethanol policy tended to fail when oil price went down. Nevertheless, Brazil has intensively researched on the engine that use ethanol; as result, flexible Fuel Vehicle (FFV) was introduced that used both petroleum oil and ethanol. This was one success of the Brazilian ethanol policy. The study was found that Brazilian ethanol policy and Thai ethanol policy were the outcome of political process. The inputs were factors that impact of the policy process of ethanol that results in ethanol policy, laws and regulations in regards to government intervention to increase production and usage of ethanol. For Brazil, the emphasis is on the government support on the development of technology, sugarcane plantation, and automobile production, whereas there is no such support in Thailand. As Thailand has used ethanol only about 4.82 percent of total gasoline, petroleum oil is still the major source of energy. Although sugarcane plantation in Thailand suffers a loss, Thailand still could not produce sufficient ethanol for export.
