Mae Sai (Thai: แม่สาย, pronounced [mɛ̂ː sǎːj]; Shan: မႄႈသၢႆ, pronounced [mɛ.sʰǎj]) 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.