The amount of usable water in two major dams, Bhumibol and Sirikit, had fallen to only 18% of capacity as of Tuesday, and people are being warned to conserve water.
The Royal Irrigation Department announced on its website that Bhumibol dam in Tak province was storing 5.457 billion cubic metres of water on Tuesday, or 41% of its full capacity of 13.462 billion cubic metres, but the usable water was only 1.657 billion cubic metres.
Sirikit dam in Uttaradit province had 4.146 billion cubic metres, or 44% of 9.51 billion cubic metres of capacity, with usable water of 1.296 billion cubic metres.
The department said the amount of usable water in the the two major dams, important for irrigation for a large number of farmers, totalled 2.953 billion cubic metres, or only 18% of combined capacity.
It said water levels in both dams had dropped continuously as the dams release water to feed demand and to maintain the ecological system before the end of the dry season over the next few weeks.
The department said some farmers were still cultivating second-crop rice and suggested they halt further planting to prevent damage to the crop.
The Meteorological Department has predicted the rainy season will arrive late this year, people are advised to preserve water for later use.
Thailand has total storage capacity of 70.326 billion cubic metres of water in dams nationwide. The overall usable water as of Tuesday was 14.946 billion cubic metres, or 21% of total capacity.