Around 40,000 B.C. - Early humans inhabit the southeast Asian region.

Around 10,000 B.C. - Distinguished ethnic groups grow in southeast Asia out of differences developed during the past 30 millennia. This assemblage of ethnic groups moves between the Yangtse Valley of central China and the islands of the Indonesian archipelago. The progenitors of present-day Thais at first occupy an area along Dali Lake of what is now Yunnan province in south China. The territory at present designated as Thailand is inhabited by three groups: Negritos (a Negroid race similar to the Australian aborigines or the peoples now found on the island of New Guinea) and Malays in the south and Lawas in the north. The Lawas, though not considered their direct progenitors, are believed to be ancestors of present-day Khmers (or Cambodians) rather than present Thais.

Around 3,500 B.C. - Proto-Thai speaking people occupy the inland river valleys of the now Guizhou and Guangxi provinces in China, east of Yunnan. Another Thai group called the Mung are found in the northwestern part of what is now the Chinese province Sichuan, north of Yunnan, and even in some west-central parts of what is today China.

Around 2,000 B.C. - Independent of each other, without uniting themselves, ethnic groups that can be regarded as ancestors of today’s Thais spread out in what is now south China. Much of the information gathered today on these Thai groups is from ancient Chinese sources. In these sources, the people regarded as early Thais are referred to as Mung, Lung, or Pa.

Around 800 B.C. - Tartars attack the western parts of China where the Thai progenitors called Lung settle. Unable to resist the invasion, they move in an eastern direction towards the Sichuan area and are assimilated into one more or less coherent group with there, Thai progenitors called Pa by the Chinese.

800 to 200 B.C. - During the Chinese Zhou Dynasty (1100-221 B.C.), the Chinese sense of identity develops. Stronger than had been the case before, the Chinese classify their own society as civilized and all foreign societies as barbarian, among them the early Thai societies. As the Chinese empire of that time does not extend into what at present are southern Chinese areas, settled then by the above named groups regarded as early Thais, Thai history during this period becomes distinguished from Chinese history for the first time. However, the early history of southern China can always at least be viewed from two perspectives: either as Thai history on what is now regarded already for a long time as Chinese territory, or as the history of south China, inhabited also by non-Chinese minority groups (there are many more than those seen as ancestors of the Thais). Furthermore, while part of the ethnic groups out of which the Thais evolved have formed a nowadays distinguished ethnic stock (the Thais), other parts of the same groups have grown into Chinese, Vietnamese, Khmer or any of the many smaller ethnic groups found today in southeast Asia and south China. Other parts of the same groups have remained as distinguished minorities under Chinese rule. Yunnan is still one of the most diversely populated provinces in China, with present-day groups named Bai and Dai. And there are a dozen more. Clear historic distinctions are not possible, and any classification of ethnic, linguistic and cultural differences always must be modified with plenty of exceptions.

Are some sexual acts good and others bad? According to what criteria? Alternatively, can consensual sexual acts be immoral, or are they outside the realm of ethics?