Surrounded by the tallest mountains in Thailand, Northern Thailand is cooler than the rest of the usually sweltering country. In the mountains at night temperatures occasionally dip below freezing, although in the plains the daily average is rarely less than 25 Centigrade or 53 Fahrenheit.

Culturally, Northern Thailand shows heavy influences from the neighboring cultures of Myanmar and Yunnan (China). The kingdoms of Lanna (centered at Chiang Mai) and Sukhothai were the first historical Thai nations.

A unified Thai kingdom was established in the mid-14th century. Known as Siam until 1939, Thailand is the only Southeast Asian country never to have been taken over by a European power. A bloodless revolution in 1932 led to a constitutional monarchy. In alliance with Japan during World War II, Thailand became a US ally following the conflict. Thailand is currently facing armed violence in its three Muslim-majority southernmost provinces.

Much of northern Thailand was for a long time off limits due to a series of Communist insurgencies and Myanmar's drug battles and civil wars spilling over the border. Both problems have been largely resolved, although caution is still advised near the border with Myanmar in the provinces of Tak and Mae Hong Son.

Separatist violence in Thailand's predominantly Muslim southern provinces prompt border closures and controls with Malaysia to stem terrorist activities; southeast Asian states have enhanced border surveillance to check the spread of avian flu; talks continue on completion of demarcation with Thailand but disputes remain over several areas along Mekong River and Thai squatters; despite continuing border committee talks, significant differences remain with Burma over boundary alignment and the handling of ethnic rebels, refugees, and illegal cross-border activities; Cambodia and Thailand dispute sections of boundary with missing boundary markers; Cambodia claims Thai encroachments into Cambodian territory and obstructing access to Preah Vihear temple ruins awarded to Cambodia by ICJ decision in 1962; ethnic Karens from Burma flee into Thailand - to escape fighting between Karen rebels and Burmese troops - resulting in Thailand sheltering about 120,000 Burmese refugees in 2005; Karens also protest Thai support for a Burmese hydroelectric dam construction on the Salween River near the border; environmentalists in Burma and Thailand remain concerned about China's construction of hydroelectric dams upstream on the Nujiang/Salween River in Yunnan Province.

Thailand is a minor producer of opium, heroin, and marijuana; illicit transit point for heroin en route to the international drug market from Burma and Laos; eradication efforts have reduced the area of cannabis cultivation and shifted some production to neighboring countries; opium poppy cultivation has been reduced by eradication efforts; also a drug money-laundering center; minor role in methamphetamine production for regional consumption; major consumer of methamphetamine since the 1990s.