The northeastern province of Sakon Nakhon experienced a sharp drop of temperature by seven degrees Celsius, the local weather forecast office reported on Wednesday.
The Sakon Nakhon Meteorological Office reported on its Facebook wall that the province saw its lowest temperature in the morning of 15C, a drop of seven degrees.
Many residents had to light fires to warm themselves in the morning.
The office said the province experienced the sharpest drop in temperature in Thailand on Wednesday.
It predicted that the temperature would drop by a further two degrees on Thursday.