Confirmation of the cremation date sets a timeframe for the coronation of Bhumibol's son, King Maha Vajiralongkorn, who ascended the throne in December but whose formal coronation has been put on hold until after his father's funeral.
Political observers say the new king's coronation will formally kick-start politics following a year-long mourning period and a general election should follow soon after.
"The palace has confirmed that the king agrees with the government's plan. The cremation day will be October 26," a senior government official, who declined be named because of the sensitivity of the matter, told Reuters.
"The funeral will take place over a five day period," Deputy Prime Minister Wissanu Krea-ngam, told reporters on Tuesday.
King Bhumibol died in October 2016 at the age of 88 following a long illness. His death ended a seven-decade reign that saw the king become a rare unifying figure in an otherwise deeply polarized nation.
Thailand has been ruled by a junta since a 2014 coup which saw the military wrest power from an elected civilian government. The military has said the coup was aimed at ending months of unrest.
The United States and others have called for a swift return to democracy in Thailand and the junta has said a general election will take place after the late king's funeral.
But some have cast doubt over the junta's election timeline.
"Political life is unlikely to resume until next year, after the cremation and coronation," a Western diplomat based in Bangkok, who declined to be named, told Reuters.
"There's an understanding among political parties that there will be no election this year. After the coronation seems the most likely time for things to start to happen."
Officials have said King Bhumibol's cremation will be a lavish affair befitting of a much-loved monarch. No budget has been publicly released for the funeral which is expected to attract huge crowds.
Thai Buddhists often wait a week or more before cremating their dead but royal funerals are exceptional.
The last royal funeral in Thailand was in 2008 for King Bhumibol's elder sister Princess Galyani Vadhana. That funeral followed a 100-day mourning period.
The king's cremation will take place at a public square in Bangkok, where an enormous wooden funeral pyre is being erected.
(Reporting by Amy Sawitta Lefevre and Panarat Thempgumpanat; Editing by)
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