Phahonyothin Road
Mae Sai District (, ; Shan: , ) is the northernmost district ("amphoe") of Chiang Rai Province in northern Thailand. 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.