This study analyzes the political economy of trade protection in Thailand during the period from 1960 to the present. It investigates the institutional aspects of trade policy making, develops simple models to describe political decisions regarding import protection, uses regressions to analyze the determinants of trade protection structure, and conducts Granger Causality tests to analyze the determinants of tariff changes over time. The Thai government is largely autonomous in tariff policy making. It seems to make tariff policy based primarily on the national plans and economic situation. Business groups' attempts to influence tariff policy making have not been significantly successful. However, the interest groups are more successful in lobbying in non-tariff policy. These trade policies have been poorly coordinated. In terms of theory, this study incorporates the government's objective function into a general equilibrium model. The government maximizes its objective function by being subject to economic and minimal political support constraints. In the national policy model, the government's preference is to industrialize the country and increase GDP. In the interest group model, the government's objective function includes personal wealth of officials and officers. For tariff policy, the regression results broadly support the national policy model as having greater explanatory power. The Thai government uses tariffs to protect the industries which produce consumer produces, the industries utilizing local raw materials, and labor intensive industries. In addition, the government maintains lower tariffs for essential goods. However, the industries with higher value added, generally have lower tariffs imposed on them--contrary to expectations. In terms of non-tariff barriers, the results suggest that the interest group model has greater explanatory power. The government is more likely to use non-tariff barriers for the industries with high concentration ratios and large numbers of workers. By using the Granger Causality test, this study found that inflation and the balance of payments did influence tariffs. The government has used tariffs to contain inflation and adjust the balance of payments in order to stabilize the economy, which in turn has provided some stability for domestic politics.