Thiam, 61, served as a minister under ex-president Henry Konan Bedie. He left the West African country after Bedie's ouster in a 1999 coup and worked for consultancy firm McKinsey, and insurers Aviva and Prudential, before his appointment as Credit Suisse CEO in 2015.
Five years later, he resigned from the Swiss bank following a major spying scandal in which he denied any involvement.
Thiam recently returned to Ivory Coast for the first time in almost 25 years to run in the leadership race of PDCI - the party of the country's first president, Felix Houphouet Boigny.
"I am a candidate for the privilege of serving you," Thiam told a cheering crowd of PDCI members at party headquarters in the financial capital Abidjan.
He will run against four other candidates in the Dec. 16 party elections. The winner has a high chance of becoming PDCI's candidate for the 2025 presidential vote.
"Thiam is the only choice because only he can lead (PDCI) to victory in 2025," said finance worker Emmanuel Katie, 31, after his speech.
The last presidential poll in 2020 ended an alliance between President Alassane Ouattara's RDR and Bedie's PDCI. Struck in 2005, it was meant to help heal political rifts that led to civil war three years earlier.
Ouattara won a third term after an election that opposition parties largely boycotted and dismissed as illegal. Clashes in the run-up to the vote and on election day killed around 35 people.
Ouattara, 81, has not yet stated his intentions for 2025.
(Reporting by Ange Aboa; Editing by Sofia Christensen and Mark Potter)
