Assuming Plastic Man would even attempt that (Not sure if he could), Thor creates extreme temperatures.
If we want to start acting like John and Plastic Man are fighting all competent like or to the best of their abilities, showings etc. we have to apply the same to Thor. Wouldn't favor the chances then personally.
Their best bet is John going for the telepathic attack right off the bat and then closing the gap quickly, jumping Thor.
Thor 4-6/10