Thitiwat Anutruttikul, the engineer in charge of construction, said he was informed by the Rural Roads Department that the tunnel should be opened to traffic from April 9 to 17, when the main road is expected to be full with Songkran revelers.
Thitiwat said the tunnel's construction was about 95 per cent finished and some small details need to be completed.
He said the tunnel would be officially opened on May 1.