The State Railway of Thailand has started excavating the 6.2-kilometre tunnel which will connect Den Chai in Phrae with Chiang Rai's Chiang Khong district, which lies on the banks of the Mekong River.
The project is part of the 323.10km-long upgrades which will see another track laid out next to the existing rail track between Den Chai and Chiang Khong, said SRT's public relations chief, Ekkarat Sriarayanpong.
