Besides gambling, there were several other social problems that plagued Siam in the period under study, the two most prominent being opium use and prostitution.1 Just as with gambling, the socio-economic changes the kingdom underwent in the nineteenth and early twentieth centuries led to a significant increase in opium consumption and commercial prostitution in Bangkok and, to a lesser extent, in the provinces. The Thai government subsequently took measures to control and limit the growth of these two phenomena, embarking upon a criminalization process similar to that of gambling: from taxation and limited control under the respective tax farms to increasing regulation and administration by the state itself, eventually concluding in prohibition. This chapter will tease out these comparisons in greater depth in an attempt to weigh the importance of the various political, economic and socio-cultural factors that determined government policies. These include the extent to which the Thai state depended on the taxation of each vice for revenue and the degree to which they were perceived to be Chinese problems. Perhaps the most obvious difference is that of timing: while gambling was more or less criminalized by 1945, opium and prostitution were not prohibited until 1959 and 1960 respectively. Moreover, prostitution was effectively re-legalized in 1966 through a semantic sleightof-hand. This raises interesting questions about the priorities of the Thai elite in regard to these three social problems. The core argument of this chapter is that the government was more concerned about gambling than either opium use or prostitution, and that this prioritization was dictated in large measure by who was adversely affected by each of these vices.