Water retained in Bhumibol and Sirikit dams, the nation's biggest reservoirs, is well below the 10-year average, the Electricity Generating Authority of Thailand (Egat) said.
The agency warned that this could affect all activities that depend on water from the two reservoirs, either for agricultural or consumption purposes.
As of Wednesday, the water reserves in Bhumibol Dam had reached 5,949 million cubic metres or 44 per cent of capacity, Egat said in a statement.
Of the total, only 2,149 million cubic metres could be released for agricultural and consumption purposes.
Available water in Sirikit Dam stood at 1,807 million cubic metres, which added to the water available in the Bhumibhol Dam came up to 3,956 million cubic metres.
Though that is 313 million cubic metres above the level in the same period last year, it is 2,600 million cubic metres below the 10-year average, Egat pointed out.
Egat assistant governor Natchaphon Phumwiangsri said the problem could worsen owing to the cultivation of water-consuming plants as well as faster-than-expected intrusion of seawater in the Chao Phraya River.
As tapwater production and irrigated areas could be affected by seawater, water has been released from the Bhumibol and Sirikit dams to ease the problem.