Moutain run-off hit and washed out three sections of the main Chiang Rai-Chiang Mai road early on Saturday.
The Doi Saket police station in Chiang Rai was alerted at 3am that the run-off had taken out sections of the highway No 118 at the kilometre markers 43, 35 and 17, making the road impassable.
The police station issued an urgent warning for motorists to instead use the Chiang Rai-Prao-Chiang Mai route.
The station said the Highway Department is urgently sending a road contractor to repair the highway.
The police station suggested the following alternative routes from Chiang Mai to Chiang Rai:
1. Highway No 11 to Lamphun and to Lampang (highway No 1), to Phayao and finally to Chiang Rai for 350 kilometres
2. Highway No 1001 to Prao district (highway No 1150), to Wiang Pa Pao, to Mae Saruay and then to Chiang Rai for 250km.
3. Highway No 107 to Fang (highway No 109), to Mae Saruay (highway No 118) and Chiang Rai for 280km.