While gender inequality in the Thai employment market is pervasive, deep-seated, and complicated, the Thai legal system provides rather limited protections against gender inequality in the workplace. Moreover, the conception of gender equality and sex discrimination are not well embedded in the Thai legal system. The aim of this study was to find out how the meaning of sex discrimination in employment should be conceptualized. This study compared the conceptualization of sex discrimination in employment in the U.S. legal system with the Thai legal protections against sex discrimination and explored American feminist critiques of the U.S. legal concept of sex discrimination to find out if the concept has been effective.