Nine provinces within the Chi and Mun river basins have been affected.
More than 260,000 rai of farmland and residential areas in nine northeastern provinces are substantially flooded, satellite data shows.
The Geo-Informatics and Space Technology Development Agency (Gistda) released its latest data from the Cosmo-Skymed-4 satellite on Wednesday.
The data showed 263,391 rai of farmland and residential areas in the nine provinces along the two river basins were under water.
Roi Et had the most flooded area with 81,191 rai, followed by Surin with 64,844 rai.
Elsewhere in the northeast, Si Sa Ket flood waters spread across 36,764 rai, in Maha Sarakham 26,705 rai, in Kalasin 14,815 rai, in Buri Ram 11,954 rai, in Ubon Ratchathani 7,200 rai and in Amnat Charoe 144 rai. Of the affected areas, paddy fields covering 147,869 rai of land were flooded.
Gistda has sent its satellite data to major agencies responsible for flood management to help with flood prevention and situation evaluation.