The western runway at Suvarnabhumi airport will be closed for maintenance between 1-6am every day until Feb 14.
The shutdown, which started on Sunday, will cause flights to be diverted to the eastern runway during the early hours of each day, said Sarinee Saengprasit, managing director of Aeronautical Radio of Thailand (ART) overseeing air traffic control management at the airport.
Both runways will be opened to traffic during the rest of the day.
However, the repairs will temporarily shorten the western runway, and only medium-size airplanes can use it.
Larger planes will be diverted to the eastern runway; it was unclear if this will cause travel delays.
Ms Sarinee said the ART has told the airlines about its maintenance activities and its consequences and asked them to change their flights accordingly.