Regarding the effect of import liberalization on the behavior of import elasticities during the process of economic development, Melo and Vogt (1984) provided two interesting hypotheses. First, as the degree of import liberalization increases, income elasticity of import demand increases. Second, as economic development continues, price elasticity of import demand increases as well due to progress in import substitution. They provided results in Venezuela in favor of these two hypotheses. Boylan and Cuddy (1987) tested these hypotheses with the experience of the Republic of Ireland and concluded that they are rejected. In this paper these Melo-Vogt hypotheses are examined in the context of Thailand, overcoming methodological shortcomings found in Melo and Vogt (1984) as well as Boylan and Cuddy (1987). Thailand is one of the most suitable countries for testing the Melo-Vogt hypotheses in the sense that it experienced transition from a highly protected underdeveloped status to export promotion with more liberalized import during the 1970s, recording rapid economic growth rates and change in the structure of the economy during its process of economic development. Despite having good resource base, the strategy pursuing export-led economic growth since 1974 placing emphasis on the manufacturing sector should have relied on the import of capital goods to enhance the production capacity. Because previous researches such as Melo and Vogt (1984) as well as Boylan and Cuddy (1987) ignored the nonstationarity issue in testing the hypotheses, their results might have been those of spurious regression. Therefore, my paper begins from checking whether the concerned variables in Thailand during the process of economic development are stationary. Using stationary variables, the Melo-Vogt hypotheses concerning the elasticities for imports are tested with the Thai experience.