The Meteorological Department has warned people to brace for heavy to very heavy rain in some areas in all regions on Saturday and Sunday.
The warning, issued at 10am Monday, said that a tropical depression was centred in the middle of the South China Sea about 600 kilometres east of Danang, Vietnam, with maximum sustained winds of about 55km per hour.
It will develop into a tropical storm on Tuesday and Wednesday with no direct effect on Thailand, said forecasters, and would make landfall in central Vietnam on Thursday and Friday.
On Saturday and Sunday, the storm will hit southern Laos and the Northeast and Central regions of Thailand.
A stronger southwest monsoon is prevailing over the Andaman Sea, the South and the Gulf of Thailand.
These conditions will cause storms with heavy to very heavy rain in some areas of the lower North, the Northeast, the Central, the East and the upper southern region of Thailand.
The Disaster Prevention and Mitigation Department reported 11 provinces are still flooded, affecting 179,074 people in 1,763 villages of 42 districts.
The 11 provinces are Prachin Buri, Sa Kaew, Chachoengsao, Sukhothai, Phitsanulok, Phichit, Ang Thong, Ayutthaya, Suphan Buri, Nakhon Pathom and Kanchanaburi.
Continuous heavy rain which hit Kanchanaburi on Sept 28-29 caused flashfloods in Lao Khwan, Huay Krachao and Dan Makham Tia districts.
Prachin Buri's Kabin Buri, Si Maha Phot, Muang, Ban Sang, and Si Mahosot districts are still flooded and 17 schools remained closed.
Floodwaters in Ratchaburi, Satun, Surat Thani, Phang Nga and Ranong provinces have completely receded and the flood situation has returned to normal.