The purpose of this paper is to identify the cause of industrialization and expansion of prostitution in Thailand. Since 1960, in which Thailand government declared the prohibition on prostitution, the government has severely punished someone involved with prostitution; the sex trade, procurers, and the behavior engaged in promotion of prostitution are regarded as a criminal act. Although the government's efforts, Thailand is known as being thinly veiled fronts for prostitution. The first step toward the solution of the problem starts from critics questioning 'What is the problem?' By understanding the cause of prevalent prostitution, we would find a clue for industrialization and expansion of prostitution in Thailand. In view of sexuality, first, the relationship between man and women was recognized as vertical structure due to the paternalism. By applying dual criteria to sexual morality, man thought that sexual desire was nature for man, but not for women. It contributed man's sexual desire for women to be spread out. Second, a matriarchal society in the northern part of Thailand was characterized. women as mother, wife, or daughter was in duty to support family. Engaging in prostitution due to the high income was inevitable for women to support family. Regardless of their willingness, prostitution was the only way for women to choose. Many women sacrificed themselves and attached significance to be able to support their family. For this reason, prostitution was thought to be one of effective means to make a living. Third, prostitution promised to compensate women for the poverty from the differential wages. With the industrialization process, many women left for the city looking for the job. It was not easy for women to get into the labor market. Most of them were miserably paid and worked in poor conditions. For this reason, prostitution was chosen as a means to make a big money.