The economic development process involves a large number of social, political, administrative, and external factors, both in terms of causes and consequences. To give a full account of those factors is impossible, while to give a sufficient account of them would require a few thick books. Since there are a number of good books on the Thai economy, as already listed in the references, it is justified to keep this paper brief and focus on salient features of the country’s economic development. For the sake of convenience, the paper refers to the National Economic and Social Development Plan periods as a reference.