Mexico moved clear at the top of Group F to put them on the brink of qualification for the knockcout stages.
Former Arsenal striker Carlos Vela gave them lead with a first-half penalty.
Vela sent goalkeeper Cho Hyun-woo the wrong way from the spot after Andres Guardado’s cross hit the outstretched arm of Jang Hyun-soo at close range
West Ham forward Javier Hernandez made it 2-0 on 65 minutes to put them firmly in control.
Hernandez cut inside his marker before guiding the ball home to finish off a lightning counter-attack after Mexico won the ball deep in their own half.
Spurs star Son Heung-min pulled one back for South Korea in stoppage time with a spectacular left-foot strike from outside the area, but it proved nothing more than a consolation.
Mexico will qualify for the last 16 if Germany fail to beat Sweden. Defeat for the world champions would see them eliminated from the competition.