Mae Hong Son was merged with Yuam, Pai and Mandala in 1910 by royal decree, and Mae Hong Son became the administrative capital, with Phraya Sonsurarat becoming the first governor of the Province. Governance was subsequently reneged in 1933 but later reinstated under the Constitution of the Kingdom of Thailand.
Mae Hong Son province itself is also linked to the Golden Triangle region of northern Thailand and featured prominently in the Japanese occupation of Thailand. Although most Japanese forces were positioned in Kanchanaburi, where prisoners of war helped construct the 'Death Railway', large camps were also set up near Namron hot springs and Ban Napakha in Mae Hong Son.
Using Thai labour the Japanese built a road from Mae Taeng, to the north of Chiang Mai, to Pai and then to Mae Hong Son. Remains of their vehicles can be seen just before entry to the town off Highway 1095. The present day route follows much of the original, 180-mile long track.