The alleged hacking took place between August 2023 and April 2025, reports say.
The chairman of a “major conglomerate” and the boss of a venture company were among the other victims, according to AFP news agency.
Police have said they plan to seek a warrant to arrest the suspect after questioning him and analysing evidence.
The suspect, who is unnamed, was based in Bangkok until the extradition.
In August last year, a 36-year-old Chinese national who is part of the same ring was also extradited from Thailand.
He was indicted in September and is now standing trial in South Korea.