Seventy percent of the land in the north is mountainous and in the past was densely forested, making overland communication difficult. As a result each valley developed slight variations in customs and language.
People practiced wet-rice subsistence agriculture and were self-sustaining, making what they needed. Customs and beliefs associated with the agricultural cycle were passed down from their ancestors.
The people of the valleys refer to themselves as the khon muang, and are of mixed origin. The first inhabitants were known as the Lawa. These people were joined by other groups moving along the trading routes of the river valleys.
Notable amongst these were the Mon, who originated from the region around Thaton in Burma. The Mon founded Haripunchai, a northern offshoot of the Dvaravati civilization that predominated in the Chao Phraya basin from the 6th - 10th centuries. By the 13th century, however, the dominant group were ethnic Tai, who had been migrating south into the valleys from at least the 10th century (some theories plausibly suggest the Tai may have been in the area long before this date). This group came to be known as the Tai Yuan.
Until the European colonialism of the 19th century, the politics of the north was dominated by the struggles with the Burmese, and between the kingdoms of Ayutthaya, Lanna and Lan Xang. Each military incursion involved forced relocation of populations to increase manpower. Thus the wars of the region served mainly to mix ethnic Tai groups. Such resettlements tended to be geographically based, resulting in subtle differences within the population of the valley to this day.
The second half of the 19th century saw a large influx of overseas Chinese coming up from the South, as well as Haw Chinese coming overland from Yunnan. Many of the latter were Muslims who had fled to the hills after the brutal Chinese suppression of the Panthay rebellion in Yunnan in 1873. At the same time the hilltribes were also moving south through the uplands.
In the mid 19th century Westerners started arriving with Christian missionaries and increased in numbers with the growth of the teak industry. The teak industry also attracted large numbers of Shan who worked all over the north for the logging companies.
The 20th century has seen large migrations of hilltribes as well as Kuomintang Chinese, who fled China after the communist victory of 1949. Finally the recent economic growth has attracted people from all over Thailand. The incorporation of Lanna into the global market place brought to an end the relative cultural isolation of the once remote northern valleys.
The main ethnic language of the north is kham muang. With differences in both vocabulary and tones, Northern Thai may be considered a different language from central Thai. Though the differences are diminishing as kham muang borrows from the state language, a person from central Thailand cannot immediately understand the northern language.