Mae Sai is the district town of Mae Sai District, located in the far northern region of Chiang Rai Province, Thailand. It serves as a significant geographical point where the Mae Sai River meets the international border.
The town functions as a major border crossing between Thailand and Myanmar, connecting directly to the town of Tachileik in Shan State via a bridge. This area forms a bi-national conurbation shared between the two countries. Additionally, the Asian Highway Network AH2 crosses the Mae Sai River to link these locations.