The singer confirmed his diagnosis in 2014 and his death on Thursday night was announced by his record label.
The singer died suddenly at his home in Surrey on Thursday, 4 January.
His death was confirmed by his record label.
In a statement, they said: “It is with profound sorrow and sadness that Cherry Red Records and Esoteric Recordings regret to announce that Ray Thomas, founder member, flautist and vocalist of the Moody Blues, passed away suddenly at his home in Surrey on Thursday.”
They added: “We are deeply shocked by his passing and will miss his warmth, humour and kindness. It was a privilege to have known and worked with him and our thoughts are with his family and his wife Lee at this sad time.”
Thomas stepped back from the band due to ill health in 1999 and in 2014 confirmed that he had been diagnosed with prostate cancer.