The Pai River (Thai: แม่น้ำปาย, Thai pronunciation: [mɛ̂ːnáːm paːj]; RTGS: Maenam Pai) is a river that originates in the mountains of the Daen Lao Range, Pai District, Mae Hong Son Province, Thailand.

There is a story that in 1477 during the reign of King Tilokaraj, who was the ruler of Lanna Kingdom.

He ordered his cousin Prince Si Chaiya to attack Ban Don.

Meanwhile, one of his white elephants fled, he ordered the soldiers to find and found that it was swimming in this river.

[1] Pai River is popular for whitewater rafting.