Typhoon Kalmaegi was moving over the South China Sea early Thursday and will reach central Vietnam by Friday, before weakening and arriving in northeastern Thailand later the same day, according to the Meteorological Department.
Sugunyanee Yavinchan, director-general of the department, said the typhoon was located in the South China Sea, about 510 kilometres southeast of the coastal city of Quy Nhon in central Vietnam, at 4am Thursday.
Typhoon Kalmaegi killed at least 140 people and left another 127 missing after unleashing devastating flooding across the central Philippines, official figures showed on Thursday.
Ms Sugunyanee said the typhoon had wind speeds of about 150 kilometres per hour near its epicentre. But it will weaken into a tropical storm and depression as it passes over Laos.
The storm will reach Ubon Ratchathani in Thailand on Friday before becoming a low-pressure system.
Due to the influence of the storm, there will be more rain and isolated heavy to very heavy rain in the Northeast, the East, the Central Plains including Greater Bangkok, and the North from Friday to Sunday. Flash floods, runoff and overflowing waterways will be possible in those regions during the same period.
Ms Sugunyanee advised small boats to remain ashore instead of going out into the Andaman Sea on Thursday and Friday due to rough seas.