Tropical Storm Trami left Vietnam for the South China Sea and was bringing heavy rain to part of the Northeast of Thailand on Monday, according to the Meteorological Department.

Sukanyanee Yawinchan, the department’s acting director-general, said Trami left central Vietnam about 4am and had moved into the upper South China Sea, its centre approximately 30 kilometres northeast of Da Nang.

Wind speed near the storm's eye was about 65 kilometres per hour and the storm was moving northeastwards at about 10kph. It would not enter Thailand, Ms Sukanyanee said.

The tropical storm would still cause heavy rain in the eastern part of the Northeast on Monday, mainly Amnat Charoen, Mukdahan and Ubon Ratchathani provinces. It was forecast to weaken on Monday and Tuesday and rains in the region would decline, Ms Sukanyanee said.

Meanwhile in the South, moderate northwesterly winds over the Andaman Sea and the Gulf of Thailand would bring persistent and heavy rain to the region on Monday and Tuesday.

On Monday, affected provinces will be Krabi, Nakhon Si Thammarat, Phangnga, Phatthalung, Phuket, Ranong, Satun, Songkhla, Surat Thani and Trang.

By Tuesday heavy rain is expected across Chumphon, Krabi, Nakhon Si Thammarat, Phangnga, Phatthalung, Phuket, Ranong, Satun, Songkhla, Surat Thani and Trang provinces, Ms Sukanyanee said.