Thanks but the credit should go to you as you provided the picture which gave me a hint where I should look for it.
Auke did some more research:
"Did some more searching and what you see in this picture seems to be part of the Mae Kuang to Mae Ngat irrigation diversion project - boring a 25.4 km. long tunnel with a diameter of 4 meter to channel water from one reservoir to another reservoir - a 5 year project according to Chiangmai Citylife Chiang Mai "