Prosecutors in South Korea demanded an arrest warrant on Thursday at around 12:40 a.m. for Kim Seong-tae, the former chairman of underwear maker Ssangbangwool who was returned home after fleeing for eight months, to look into links between Kim and President Yook Suk Yeol's political opponent.

Kim went through 13 hours of interrogation by prosecutors in Suwon, Gyeonggi Province, beginning Tuesday afternoon. The interrogation resumed at 10 a.m. on Wednesday.

The crime ring member-turned-entrepreneur faces multiple charges of embezzlement, market manipulation and smuggling funds to North Korea, among others.

Kim, 55, fled to Singapore to avert the prosecution's probe in May 2022. He was arrested by police in Thailand last week.

The probe into Kim puts Ssangbangwool under the spotlight over links between company executives -- possibly including Kim -- and the main opposition Democratic Party of Korea’s leader Lee Jae-myung. Kim denied the links upon his arrival at Incheon Airport on Tuesday. Lee has also denied such links.

Prosecutors suspect that Kim had created a slush fund with proceeds from convertible bond transactions for two years until 2019 -- deals that had involved Kim's alleged acts of stock market manipulation -- and that part of the fund was used to cover attorney fees for Lee.

Kim is accused of embezzling some 3 billion won ($2.4 million) from Ssangbangwool Group to buy securities issued by the company.

Kim is also allegedly involved in Ssangbangwool's $6.4 million of money transfers to China over the course of two years until 2019. Prosecutors suspect part of that money was used to lobby North Korean officials for business rights there, including the mining of rare earth minerals. A South Korean entity's unauthorized money transfer to North Korea is punishable under the Foreign Exchange Transactions Act.

The mining rights of Ssangbangwool affiliate SBW Life Sciences, then known as Nanos, were allegedly used to manipulate the company’s stock prices in May 2019.

Ssangbangwool's ties with North Korea began to unfold when Lee was serving as the governor of Gyeonggi Province.

Lee then sought to explore business ties with North Korea. On the agenda was Gyeonggi Province's project worth 5 billion won to build a smart farming system in North Korea. Prosecutors are looking into how Ssangbangwool covered the cost of the project, although the local government was responsible for the expense.

Kim is not the only Ssangbangwool Group executive suspected of having ties to Democratic Party head Lee.

Lee Hwa-young, the ex-vice governor of Gyeonggi Province and a close aide to main opposition party leader Lee, was formerly an outside director of Ssangbangwool.

The vice governor then led the local government's North Korea deal, mainly involving Ssangbangwool and the nonprofit organization Asia Pacific Peace Exchange Association. He now faces charges of taking bribes from Ssangbangwool.

Meanwhile, An Boo-soo, head of the Asia Pacific Peace Exchange Association, was a board member of SBW Life Sciences. The organization is suspected of smuggling currency to North Korea.

Moreover, lawyers who represented Lee and his wife in past litigations, including one centering on allegations of an election law violation, had been outside directors of Ssangbangwool. Prosecutors are looking into whether the cost of hiring the attorney -- suspected to be over 2 billion won -- had been paid by Ssangbangwool instead of Lee himself.

Another key figure in Ssangbangwool, former Vice Chairman Choi Woo-hyang, was arrested for his involvement in a high-profile land corruption scandal in Seongnam, Gyeonggi Province.

Prosecutors are to interrogate Lee Jae-myung over his alleged involvement in a scandal surrounding a residential complex development project, which broke ground during his tenure as mayor of Seongnam, before he was governor.

The project had allowed inexperienced asset management company Hwacheon Daeyu to take dividends disproportionate to the shareholding structure of the land developing consortium. Prosecutors are investigating who the recipients of the dividends were, and Lee Jae-myung on Wednesday said he is to appear at the prosecutors' office on Jan. 28 regarding his alleged ties to the lucrative project.

This comes as the latest development of the widening prosecutorial probe into the main opposition leader. Allegations range to include involvement in wrongdoings in the North Korean project, involvement in land corruption in Seongnam and solicitation of bribery to a third party.

Lee Jae-myung has repeatedly denied all the allegations.

On Tuesday, the Democratic Party leader posted a statement to prosecutors regarding the third-party bribery charges. He said companies' money transfers to the city's soccer team Seongnam FC -- suspected as a third party for receiving bribes from six companies -- cannot be construed as graft, given that what the companies did in exchange for their "advertising expenses" with Seongnam FC was for the public interest, not for himself.