The fires broke out on Khao Chaphlu Mountain in Muang district on Wednesday. The steep mountain terrain prevented firefighters from reaching the blaze, which quickly spread to the adjacent Khao Laem forest.
The Centre of Disaster Prevention and Mitigation and other agencies are collaborating in a desperate effort to stop the blaze from spreading to other areas.
The forest fires have damaged more than 700 rai [112 hectares] of land in the forested area, especially behind Chulachomklao Royal Military Academy.
Deputy Prime Minister Prawit Wongsuwan recently cancelled his trip to the academy via helicopter.
After taking a helicopter to survey the scene, Chaiya said only a few fires still burned in the forested area. He added that only a few animals lived in the forest.
"If nothing goes wrong, the mission [to extinguish the fires] should be completed today," he said.
He also assured that the fires would not spread to Saraburi province, adding that helicopters are extinguishing the fires from above.