My trainer tells me to literally mimic the thai knee.
SO, if you know how throw the thai knee throw the strike slow.
say for example you want to hit the body, stop your knee strike around mid-level which would more than likely be the height of the opponent's crotch.
now if you want hit the face stop the knee right around the height of the abs on your opponent.
Throughout life there are bumps along the way some may be painful...others not...who gives a damn in the end you'll still die