The unstoppable German, 26, could retain the title in Japan next week if he wins and Ferrari rival Fernando Alonso finishes outside the top eight.
Not even two appearances by the safety car, or the worrying sight of his team-mate Mark Webber climbing out of his burning Red Bull, was enough to stop Vettel’s fourth win on the bounce.
He took the chequered flag 4.224sec ahead of Kimi Raikkonen of Lotus, who just beat team-mate Romain Grosjean to the line for second.
Sauber’s Nico Hulkenberg and Mercedes’ Lewis Hamilton, who started second on the grid, were fourth and fifth.
Vettel’s third win on the trot in Korea means he has racked up 272 points, a mammoth 77-point lead over nearest challenger Alonso, who came home sixth at Yeongam.
“I’m loving what I do,” Vettel, booed at previous races because of his dominance, told the crowd from the podium.
“I’m trying not to think about it to be honest,” Vettel told a post-race press conference, flanked by Raikkonen and Grosjean, when told he could win the title next week.
“There are still a lot of points to get even though it looks very good for us. There is a chance for Fernando (Alonso) so we need to stay on top of our game.
“To be honest, as I said on the podium, we are just having a good time. We enjoy the fact the team is working very well, the car is working — it’s very on the edge, to honest, probably more than you think from the outside.”
The real battle on an overcast but dry afternoon next to the Yellow Sea was behind the German, with Hamilton and Grosjean duelling for long periods for second.
Hamilton’s Mercedes team-mate Nico Rosberg was also in the mix before a problem saw sparks dance spectacularly from the front of his car as he overtook Hamilton on lap 28.
An extended pit stop saw the German rejoin in midfield and he had to settle for seventh, with McLaren’s Jenson Button eighth.
Felipe Massa of Ferrari and Sergio Perez of McLaren rounded out the top 10.
Vettel was already streaking away at the first hairpin, where there was early drama when Massa spun around, causing his team-mate Alonso to run wide with Button and the Force India of Adrian Sutil suffering minor damage.
The Brazilian Massa, who started sixth on the grid, found himself dumped down to the back of the field.
There was another hair-raising incident on lap 31, when Perez saw a front-right wheel explode on the straight, catapulting rubber dangerously over the track and bringing out the safety car.
But no sooner had the safety car departed than it was back out on lap 38 when Sutil was again in the thick of it, appearing to spin and take out Webber.
The Australian’s Red Bull glided off the circuit and went up in flames, but Webber — who qualified third but started 13th on the grid because of a penalty — clambered out safely.