Commonly included among the highland people were the ethnic groups living in the mountains of northern and northwestern Thailand in the area known, because of its illegal opium production, as the "Golden Triangle." Until the 1970s, the Thai central government tended to regard these groups chiefly as opium cultivators engaged in illegal activities. Since that time the highland minorities, through their own efforts and government-organized crop substitution projects, have become involved in the legal market economy of the country.

Among the larger groups of highland people were the Karen (Kariang, Yang), Hmong (Meo, Miao), Mien (Yao), Lahu (Mussur), Akha (Kaw), and Lisu, or Lisaw (see fig. 10). Some of the smaller groups preceded the Tai-speaking peoples in the area, but many were relative latecomers. Through natural increase and immigration, the population of the highlands increased from approximately 100,000 in 1948 to about 700,000 in the late 1980s, according to Ministry of Interior estimates. This population growth led to a significant increase in the number of landless people in the highlands. As a result, many of the landless began cultivating forest reserves, thereby accelerating the depletion of the country's forestland.

The varying estimates for specific groups in some cases reflected the tendency of estimators to include only those still living in relatively isolated mountain communities, whereas other observers might include some or all of those who had come down from the mountains and were at various points in the process of becoming Thai. Observers noted that for some groups, more individuals were in the process of assimilation than remained in the mountain communities that were their traditional homes. The languages spoken by the hill peoples fell into three broad categories: Tibeto-Burman (a subfamily of the larger Sino-Tibetan language family), Mon-Khmer (a subfamily of the Austro-Asiatic language family), and the small Miao-Yao language family. The language of the most numerous of these hill peoples, the Karen, was generally considered Sino-Tibetan, but some authorities included it in the subset Tibeto-Burman, or placed it in a category of its own. The other languages included in the Tibeto-Burman category--Akha, Lisu, Lahu, and Jinghpaw (Kachin)--have been estimated as ranging from a few hundred speakers (Jinghpaw) to about 25,000 speakers (Akha).

The category of Mon-Khmer included a number of highland groups: the Kui (called Soai by the Thai), which totaled between 100,000 and 150,000 in the mid-1960s the Tin, about 20,000 and several smaller groups, including the Lua (also called Lawa), about 9,000 the Khmu, about 7,600 and the Chaobon, about 2,000. The Kui were said to be largely assimilated into Thai society. The figure for the Khmu pertained only to those presumably living in the highlands in a more or less traditional setting. Substantial numbers were said to be pursuing a Thai way of life.

The Miao-Yao languages were spoken by two peoples, the Hmong and Mien, both originally from China (848 (the terms Miao and Yao are Chinese). There were Hmong and Mien still living in China as well as other Southeast Asian countries. Called Meo by the Thai, the Hmong began to arrive in Thailand in the late nineteenth century, and some continued to migrate directly from China or other neighboring states, particularly Laos. Numbering about 50,000 in 1970, the Hmong were one of the largest groups of hill peoples. An additional 40,000 Hmong fled from Laos to Thailand in 1975, but by the late 1980s many of these had migrated elsewhere, some going to the United States. The Mien were even more recent arrivals, most of them having come from Laos after 1945. Their numbers were estimated at 30,000 in the 1980s. These two groups, particularly the Hmong, were among those affected by the security operations of the Thai government that began in the mid-1960s. These actions occurred in part because the Hmong, like other mountain groups, were said to be destroying forests in the course of practicing their traditional shifting cultivation, and in part because their chief cash crop was the opium poppy (see State of National Security , ch. 5).

Data as of September 1987