Colin Clark added a goal and an assist for Houston, which moved into a tie with Kansas City at 27 points.
Seattle (38 points) stayed third in the Western Conference.
Ching made it 2-0 in the 23rd minute on a header from about six yards off a cross from Geoff Cameron on the left.
Alvaro Fernandez cut the lead to 2-1 with a penalty in the 37th minute after Fredy Montero was taken down in the box by Corey Ashe.
Ching extended the lead in the 70th after getting a cross from Clark from the right box in front of an empty net for the tap-in.