Paris Saint-Germain's Lee Kang-in scored the only goal just after the hour in Seoul when he fired home from close range, with skipper Son Heung-min heavily involved in the build-up.

South Korea were already into the third and final stage of qualifying as group winners, but China's defeat leaves them in serious trouble of an early exit.

Thailand will leapfrog China into second in Group C - and a place in the next phase - if they defeat Singapore and overturn China's slightly superior goal difference.

With no more games to play in the second qualifying round, China's defeat left them on eight points and a goal difference of zero.

Thailand go into their home fixture against basement side Singapore later Tuesday with five points and a goal difference of minus two.

South Korea may already have topped the group but they had more of the ball for much of the contest at Seoul World Cup Stadium.

Midway through the first period Son, the Tottenham attacker, fired a free-kick from distance onto the roof of Wang Dalei's goal.

The Koreans, under caretaker coach Kim Do-hoon, continued to put pressure on the visitors' defence but it was China who could have taken the lead 10 minutes before the break.

Xu Haoyang whipped in a delicious free-kick from the right but Jiang Shenglong could only flash his unmarked header wide of the home goal.

Under then-coach Jurgen Klinsmann, South Korea were comfortable 3-0 winners away at China in November, with Son scoring twice.

Themselves under a new coach in Croatia's Branko Ivankovic, China held on for an hour this time, until Lee struck to leave their World Cup dreams in danger.

Son crossed from the left and the ball eventually fell to Lee near the penalty spot, the attacking midfielder arriving at the perfect time to rifle the ball into the net on 61 minutes.