Although Thailand has established and maintained an immunization policy for children regardless of ethnic origin, the National Expanded Program on Immunizations (EPI) has not been able to reach many children of migrants, due to a lack of information on both the size and location of this population. This article presents the results of a study of the migrant population that provides recommendations for improving EPI coverage. Quantitative and qualitative data were collected from 133 migrant women from Myanmar living in the Bangkok Metropolitan Area (BMA). From the results of the study, it is estimated that there are 39,292 children of migrants aged 0-14 years living in the BMA. Among these, approximately 22,907 children are in the age range of 0-2 years, most of whom were born in Thailand. Results reveal that although vaccine services for children of migrants is a major initiative of the Thai health system, immunization coverage is less than that of Thai children and that of non-migrants in their countries of origin. This low coverage level indicates that human migration is a significant factor limiting access to vaccine services. The study also generated key recommendations for better immunization services to children of migrants living in Thailand