In Ubon Ratchathani, residents of some 1,600 households evacuated to higher ground at roadsides as the water level in the Mun River continued to rise and overflow its banks, flooding the provincial seat and Warin Chamrap district.
Meanwhile, the Mekong River is also rising and is about to overflow, causing difficulties in diverting water from the Mun into the Mekong.
In Chaiyaphum, the swollen Chee River has inundated the provincial seat for more than a week. A two-kilometre section of the Chaiyaphum-Sikhiu Road, the main road leading to the capital, is under some 50cm of water.
The flooding has extended to the town's business district and market traders have doubled prices of commodities.
In Nong Khai, heavy rain Monday night triggered flooding in the provincial seat.
Heavy rain and small capacity drainage ditches in Nong Khai municipality led to a slow release of flood water into the Mekong River, resulting in flood conditions in the city and water half a metre deep in the business district.
Residents built sandbag embankments as the roads are higher than their homes, and many shops have been damaged.
In August, the business district was impacted by tropical storm Nock Ten, with the ensuing flooding causing damage in excess of Bt100 million. Businesses and residences have yet to be rehabilitated in the wake of the last round of storms and floods.
In Maha Sarakam, the Chee River has risen at an average of 10-15cm per day for several days. The high water level poses a flood threat to low-lying areas and the situation is being closely monitored as the weather bureau has warned of heavy rains. The rising water in the Mun River can flow in reverse into the Chee River.
More than 13,000 households in Maha Sarakam's six districts have been affected by flooding with 48,000 rai (about 19,000 acres) of crops damaged so far.
The Meteorological Department Tuesday warned that more rain and isolated heavy rain is likely over the Central region, the lower Northeast, the East and the South west coast through Thursday.