Pacquiao issued a statement on Wednesday through his office as a senator, endorsing a letter from the country's Games and Amusements Board for a thorough review of the judges and referee who oversaw the bout.
"I had already accepted the decision, but as a leader and, at the same time, a fighter, I have the moral obligation to uphold sportsmanship, truth, and fairness in the eyes of the public", added the eight-time world division champ.
In 2012, the WBO also reviewed Pacquiao's controversial split decision loss to Tim Bradley Jr. a the MGM Grand by having a five-man panel watch the entire fight without audio.
"(That was my) last fight (with Top Rank)", said Pacquiao, who dropped a close unanimous decision at Suncorp Stadium in Brisbane.
Pacquiao attached a copy of the letter to his own statement. "Horn provides a rematch clause, which the WBO is in accordance if the promoters decide to move forward".
However the decision has caused uproar, with many claiming Manny deserved to win the fight, but Valcarcel has pointed out that there is no precedent for his organisation to step in.
The WBO sent out a tweet on Tuesday in relation to the request, stating that there was no fraud or rules violation by the referee or the judges that would result in an overturning of the outcome.
Likewise, Pacquiao lashed at referee Mark Nelson's carefree attitude against Horn's rough tactics.
If a rematch with Pacquiao fall through, Horn has also mentioned the possibility of unifications with IBF champion Errol Spence and WBA champion Keith Thurman - both of them are based in America.
"The problem here is that the referee, I don't know if he did it deliberately or he just did not have experience, he just allowed it and did not even give any warning for how many times", Pacquiao said.