The Thai Meteorological Department has warned people to brace for the impact of Typhoon Vamco over the weekend.
As of Friday, the typhoon had killed at least 42 people in the Philippines, as residents returned to devastated homes following the worst flooding in years in Manila and nearby provinces, according to news agencies.
Flooding on the largest island, Luzon, caused landslides, cut off roads and forced many to flee their homes.
Tens of thousands of people have sought shelter in evacuation centres, including in the capital Manila.
The typhoon, known locally as Ulysses, is the 21st storm to hit the country this year.
It comes just one week after the Philippines was hit by Goni, the most powerful typhoon seen in the country in seven years.
The Thai weather agency said the eye of the storm yesterday was in the South China Sea, about 500km east of Danang in Vietnam and was expected to make landfall there tomorrow.
Heavy rain is therefore expected in the North and the Northeast of Thailand today and tomorrow, it said.
Meanwhile, heavy rain in the South has flooded many areas in Chumphon province. Areas in all eight districts were affected.
Sawi was hardest hit with parts of the Asia Highway underwater.