In Thailand, the system of social security has been developed since 1901. The system has extended little by little and it is still far from perfect (in term of the OECD standards). The current social security systems of Thailand have at least three policy issues to be improved. First, the coverage of social security for private employees is low. Prior to 2002, when the Social Security Act was enforced to private enterprises employing at least ten workers, many employees were not covered by the mandatory social insurance system. After the Social Security Act had extended to cover micro enterprises (employing less than 10 employees) in 2002, the system could not enforce about 20 percent of private