The appeal is part of a campaign by the 60-year-old Frenchman to get back into the election for a new leader of scandal-tainted FIFA to be held on February 26.
Platini appeared before the CAS tribunal in Lausanne with his lawyers in a bid to get the suspension ordered in October provisionally lifted.
"I will say nothing more than I have already told you: the truth, all the truth and nothing but the truth," Platini told reporters with a half smile before entering the tribunal.
Sport's highest appeal court has promised a decision by Friday "at the latest."
FIFA's ethics committee suspended the boss of European confederation UEFA in October after he was linked to a criminal probe by Swiss prosecutors.
According to Platini's lawyers, FIFA's ethics watchdog wants the French football legend banned for life.
Platini has gone to CAS in a bid to get the suspension temporarily lifted. The Frenchman and FIFA president Sepp Blatter will appear before a FIFA appeal committee on December 16-18 for the main challenge against their 90-day suspensions.
Platini's decision to give up on his dream of becoming
FIFA president leaves five declared candidates.
They are Asian football head Sheikh Salman bin Ebrahim al-Khalifa of Bahrain, South African politician and tycoon Tokyo Sexwale, former FIFA vice president Prince Ali bin al Hussein of Jordan, UEFA general-secretary Gianni Infantino and Jerome Champagne, a former FIFA assistant general secretary from France.
Platini, a FIFA vice president, and 79-year-old Blatter were banned from all football-related acivities by FIFA's ethics committee on December 21.
"I'm struggling to understand. Why? How did we get to this? I did some work, I asked to be paid, I sent an invoice, I was paid, I paid my taxes on that. That was in 2011," he told AFP when the ban was announced.
"There was a debt that was settled, full stop! Then, in 2015, the Swiss court wanted more information.
"Then it took off at FIFA and a lot of people at FIFA are happy that this issue happened.
Platini repeated his suspicions that the timing of the ban was a deliberate attempt to prevent him from standing in February's election.
"What was the FIFA ethics committee doing between 2011 when I was paid and 2015? Was it sleeping? Suddenly it wakes up," he scoffed.
"Ah yes, it wakes up in a FIFA election year when I'm a candidate. It's amazing!"
Later yesterday, UEFA said in a statement emailed to AFP that it "continues to support the right of Michel Platini to due process and the opportunity to clear his name".
