Recently, eucalyptus farm forest has rapidly expanded in Thailand, especially in the eastern and northeastern regions. Based on a field survey in two neighboring villages in Khon Kaen province, northeast Thailand, this research examines how recent economic changes have affected the expansion of eucalyptus farm forest, and how differences in the villages arose during the expansion process. Two kinds of analysis: static statistical analysis of the households and historical dynamics of the villages since the 1980s, were conducted. First, it was found that there were three stages of development in these villages: the factor substitution process for land, the factor substitution process for labor, and the process after the economic crisis. Second, differences in planting behavior arose as differences of response to the second stage of development. Both the history of each village and socioeconomic attributes of each household affected the response. This indicates that the villagers' eucalyptus planting was one economic-rational response to the recent changes in the rural economic environments caused by rapid economic growth. Finally, it was also found that recent land transactions, especially after the economic crisis, tend to differentiate the management scale of eucalyptus farm forest. Farm forest management is, thus, entering into another stage.