In the 19th century, there existed a road, that took several days to travel, going from Chiang Mai to Pai. The area now known as Pai was then called Ban Wiang Tai. New immigrants settled the areas near the system of trails between Pai and Mae Hong Son.
In 1943 the Japanese undertook a number of project for the purpose of developing more efficient routes of transport for troops and equipment between Thailand and Burma to bolster their planned raids of Imphal and Kohima.
One of these projects was the Burma Railway, also known as the Death Railway, that traverse Kanchanaburi. Another project improved the existing trail between Pai and Chiang Mai, turning it into an actual road and improvements to the systems of trails to Mae Hong Son. How the Japanese got across the Pai River 10 km (a bit more than 6 miles) southeast of Pai is not currently certain. A bridge currently at the site was built after the war and titled ‘World War II Memorial Bridge’. The bridge was build by the as a one of a series of road improvement projects by the Thai government and has since been extended twice. In early 1944 the Japanese abandoned their attempt to build a connection between Pai and Chiang Mai. It had become apparent that they would not be able to finish the project before the anticipated raid on Imphal, though the incomplete road did allow a path for the Japanese to flee after they were soundly defeated in Imphal and Kohima.
In 1967, the government of Thailand began work on the road between Chian Mai and Mae Hong Son via Pai, the highway now known as Route 1095, though the road wasn’t completely paved until the 1990s.
The modern history of Pai is characterized by waves of immigrants. Though the majority of immigrants consisted of the Shan and Lanna peoples, immigrants from Karen showed up in the 18th century and the early 20th century saw Lisu and Lahu immigrants from southern China. In 1950, Muslim traders began to establish a trade route and in the 1960s, Kuomintant refugees escaping Mao Zedong organized a comunity in Pai. Most recently, refugees from Burma’s Shan State escaping unrest induced by the Burmese Junta arrived to work in Thailand.