Park officials said most of the burned forests were located in the Ob Luang National Park.
The officials said fires started almost simultaneously in the three districts of Hot, Chomg Thong and Mae Cham.
At press time, the fires were still raging uncontrolled. Officials blamed torching by local villagers looking for edible foods and spillovers from burning of farm leftovers for the fires.
At night, flames were clearly seen at the burning spots, turning the sky red. But during the day, white smoke was seen covering the spots where the blaze had consumed most of the dried leaves and grass.
Thossapol Puan-udom, deputy Chiang Mai governor, said on Sunday that he was still closely overseeing the operations to put out the blaze.
He also blamed the heat and dry weather for many of the fires, which he said, occurred on high mountain spots and made it difficult for fire-fighters to reach those areas.
Thossapol said the fire command centre of Hod district was requesting air operations from the Natural Resources and Environment Ministry to help fight the blazes.
Thossapol said the ministry in return was seeking help from the Third Army Area to provide aircraft to support the fire-fighting.
Meanwhile, the Chiang Mai PM2.5 monitoring centre reported that 69 hotspots were detected on Sunday and 38 of them were in Hot district, 13 in Mae Cham, 6 in Doi Tao, 4 in Chomg Thong, 3 in Mae Taeng, 2 in San Sai, and one each in Prao, Mae Kwang and Chiang Dao districts.