![Oh Se-hoon, the mayor-elect of Seoul, receives a bouquet of flowers as he arrives at Seoul City Hall in Jung-gu on Thursday morning. Oh, the People Power Party candidate, staged a come-from-behind victory over Democratic Party of Korea candidate Jeong Won-oh in the Seoul mayoral race — the marquee contest of the June 3 local elections — winning by a narrow margin to claim an unprecedented fifth term as Seoul mayor. [Photo by Lim Se-jun]](https://wimg.heraldcorp.com/news/cms/2026/06/04/news-p.v1.20260604.cbd9ab807059423f828d2673e8d4ac2e_P1.jpg)
A user on the U.S.-based blockchain prediction platform Polymarket won roughly $160,000 (about 240 million won) by betting on Oh Se-hoon's victory in the Seoul mayoral race during the 9th National Simultaneous Local Elections. South Koreans who place bets on Polymarket or similar platforms, however, face potential criminal liability — gambling charges under the Criminal Act carry fines of up to 10 million won.
According to Polymarket on Thursday, a user operating under the nickname "JackInT" accumulated the winnings after placing large bets on candidates in several of the country's most competitive local races ahead of the elections.
The user's total position value reached $321,500 (about 482.25 million won), and the account recorded a single-day profit and loss of $97,863 (about 146 million won). The user posted the biggest gains on the Seoul mayoral race while suffering losses on the Busan mayoral contest.
On the question of whether Oh Se-hoon would win the Seoul mayoral race, the user selected "Yes" and earned $160,102 — a return of 106.41 percent, more than doubling the original stake.
Analysts say the high payout reflected the relatively low odds assigned to Oh at the time, after a joint exit poll by the three major broadcasters showed his rival Jeong Won-oh leading 51.4 percent to 46.0 percent. The longer the odds, the larger the potential payout.
However, the user's predictions went wrong in Busan.
Bets on Park Heong-joon winning the Busan mayoral race cost the user $9,997 — a loss of 97.9 percent — while a wager that Jeon Jae-soo would not win resulted in an additional loss of $5,966, or minus 98.39 percent. The user lost a total of roughly $16,000 (about 24.45 million won) on the Busan races alone.
Polymarket is the world's largest decentralized prediction market platform, where users bet virtual assets on the outcomes of future events spanning politics, sports, economics and weather.
South Koreans who participate in Polymarket or similar sites risk prosecution for gambling under the Criminal Act, which carries fines of up to 10 million won. Under current law, any betting platform not explicitly permitted — such as Sports Toto, operated by the Korea Sports Promotion Foundation with a per-bet limit of 100,000 won — is considered illegal, and users can be charged with gambling.
yeonjoo7@heraldcorp.com
