This chapter argues that as the European powers moved into South, East, and Southeast Asia in the second half of the nineteenth century, the Thai kingdom, while remaining formally independent, was drawn into the diplomatic and economic orbit of the British Empire. One of the effects of this shift was that the old courtly styles of conduct were challenged by new bourgeois ideals of how to behave. This led to the emergence of the concept of the phu di, the gentleperson. The key aspect of the concept of the phu di was that one did not have to have been born into a noble family in order to perform good behaviour. The Thai court promoted the new ideal especially in what would become Thailand’s most famous manners manual, Qualities of a Gentleman (the manual continues to be published today). The chapter outlines how the Thai gentleperson ought to behave. The chapter also argues that from this period there were intense debates about what constituted good conduct, which was a reflection of the growing political tensions between the aristocracy and Western-educated civil and military government officials.