In his statement, Panelo noted how Pacquiao started the year by successfully defending his WBA welterweight belt over American Adrien Broner, and now scoring another victory just six months later.
Despite Pacquiao rejecting the claims, Amir Khan is adamant he will fight the 40-year-old in Saudi Arabia later this year.
Thurman's effort was impressive on paper: He landed slightly more punches than the famously active Pacquiao, and his 192 power punches landed were the most by any Pacquiao opponent in his 43 fights that were tracked by CompuBox.More news: Acacia Mining agrees to offer from parent Barrick Gold
But Thurman gathered himself and soundly beat Pacquiao through the middle rounds, forcing Pacquiao to show off his durable chin.
The eight-division world champion said he will now return to the Philippines to resume his work as a senator before deciding on his next move inside the ring.
Thurman, 30, fell to 29-1 after promising he would make Pacquiao "disappear".
With his second victory on the year, Pacquiao became the oldest welterweight in the history of boxing to win a major title.More news: Second airline suspends flights to Cairo over 'security concerns'
The younger Thurman appeared to be gaining momentum as the fight drew on, backing up Pacquiao with a clean combination in the eighth.
The body shots continued from Pacquiao in the tenth round and he again looked to have the champion in intense pain with many left stunned that Thurman was still standing. I wish I had a little bit more output to go toe-to-toe.
But Pacquiao slipped out of danger and took control of the center of the ring. Thurman said he would do to Pacquiao what Pacquiao had done a decade ago to the aging De La Hoya: give him a savage beating and send him into retirement.More news: British Open Final Round Betting Roundtable: Can Shane Lowry Be Caught?