The town of Mae Sai is a major border crossing between Thailand and Myanmar.

Asian Highway Network AH2 (Thailand Route 1 or Phahonyothin Road) crosses the Mae Sai River to the town Tachileik in Myanmar.

The westernmost part of the district is dominated by the hills of the Daen Lao Range, the most important one is the Doi Tung with the Wat Phra That Doi Tung temple on top.

The minor district (king amphoe) Mae Sai was created on 1 March 1939, when the two tambons Mae Sai and Pong Pha were split off from Chiang Saen District.

[2] The district is divided into eight subdistricts (tambons), which in turn are further subdivided into 92 villages (mubans).