Somkid Tuaboontham, chief of the Doi Inthanon Park rangers, said the frost could be seen from Kew Mae Pan Park to the top of Doi Inthanon and had been occurring for three consecutive days.
Meanwhile, the Disaster Prevention and Mitigation Department yesterday warned people in the Southeast to prepare for heavy rain and the danger of floods from today to December 25.
People living near hillsides and waterways in Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Yala, Pattani and Narathiwat should prepare for heavy rain, flash floods and possible landslides, it warned.
There will also be strong wind and high waves in the Gulf of Thailand, and hence all ships should proceed with caution and small boats should stay ashore until Sunday, the department said.