The work was completed last night after about 100 workers and engineers laboured for three days, their work hindered by continuous heavy rain.
Train services could not resume this morning, as the soggy soil may not be safe. A test run with an empty train is due to be conducted before the service resumes.
On Saturday, a flash flood caused a sinkhole under the railway track, leaving it dangling in the air and bringing a halt to LamphunChiang Mai trains.