Abstract: This study, uses a firm-level survey to examine the economic impacts of foreign migrants on Thai firms. Estimations show that an increase in unskilled migrant workers should cause a drop in labor productivity, a reduction of a firm’s probability of R&D investment and a reduction of skills training. These negative impacts are based on evidence of increased use of labor-saving technology whereby the employment of unskilled immigrants encourages firms to rely on cost competiveness based on low production costs rather than value-added (or long-term) competitiveness, such as R&D investment and skills development. Even though immigration benefits, Thai producers by allowing them to maintain price competitiveness by lowering wage costs, this is merely a short-term benefit and one that jeopardizes long-term economic development.