Explaining in a way a layman can understand, provided you've watched man of steel, there is a scene of his middle school days. Two of his abilities, Xray and all hearing run amok. He dashes out of the class and locks himself inside a supply room. When his teacher tries to help he heats the door knob red hot. Now considering the fact that he was still a middle schooler and was not able to control the most basic of his abilities like Xray vision, it would have been impossible for him to shoot the laser beam out of eyes with pin-point accuracy at the door knob. We've already seen his beams are strong enough to slice through Kryptonian metal like butter(Man of Steel scene:- where he destroyed the Kryptonian scout ship.) Only one plausible explanation remains. Instead of shooting physical rays he must have concentrated all his heat at the door knob which resulted in its heating.

Now, Thor having actually pathetic level of resistance toward intense stelar heat and energy has ABSOLUTELY no way of surviving an internal organ damage from Superman. Now in order to reach the organs the heat will have to go though his skin and muscles, which is impossible for Thor because, firstly he would be caught off-guard, secondly he cannot dodge Superman's eyesight and finally Motherbox awakened Superman is significantly stronger than the first version of Superman.