By The Nation
No one was injured in the incident on Rangsit-Nakhon Nayok Road in Thanya Buri district, but even by 11am, only one lane was open.
Motorists were advised to find another route.
Pathum Thani Highway Office director Rung Buayairaksa said the 36-metre-long beam was being hoisted into place when it struck another one already sitting on pillars.
It fell onto machinery on the road surface, but workers were able to scramble out of the way.
The fallen beam could not be moved before morning rush hour, resulting in a severe traffic jam.