Over 4,000 people in Ubon Ratchathani have been evacuated after recent flooding was set to intensify as Typhoon Noru hit northeastern Thailand on Wednesday night.

Noru reached Salavan province in Laos as a tropical storm in the afternoon. It was forecast to cover the lower part of the Northeast over Ubon Ratchathani's Khong Chiam district by Wednesday evening.

The storm would gradually downgrade to a depression and a strong low-pressure system. It will bring heavy rain and strong winds to all regions.

Flash floods and runoff are possible, the Meteorological Department said.

At least 12 provinces, mostly in the northern and northeastern regions, were already experiencing flooding caused by downpours that have pounded the country since last week.

The Northeast's Mun River burst its banks, flooding villages and farmland in 14 districts, and forcing the evacuation of some 4,169 residents to high ground and temporary shelter centres. More than 99,000 rai of farmland was damaged.

Ubon Ratchathani airport was hit by heavy rain and strong winds on Wednesday, making it impossible for aircraft to land. A Nok Air flight departing from Don Mueang airport had to circle around Ubon Ratchathani airport three times and was eventually forced to fly back to Don Mueang.