Is satan able to read our thoughts? Does he know what we are thinking?

I think that we can emphatically answer your question “No,” for a couple of reasons. First, Satan is not God, and thus he does not possess any of the attributes of God. He is not, for example, omnipotent, because his power is limited to what God allows (Job 1 & 2; Luke 22:31-32). Neither is he omnipresent, though he appears to have a good “network” of demons. To be able to read one’s thoughts seems to be a manifestation of omniscience, which our Lord demonstrates (Matthew 9:4; 12:25). Further, the temptation of our Lord by Satan would have been a futile effort, had Satan been able to read the thoughts of the Master. The temptation was a huge failure for Satan, who arrogantly attempts it anyway. I doubt that he would have made a spectacle of himself before his fallen ones had he known our Lord’s thoughts, and how foolish his effort would be. Further, if Satan could have known our Lord’s thoughts, he would have known the future, and that the cross would not be a victory, but a defeat. Further, I find no instance in the Scriptures where Satan reads men’s thoughts.

My own inclination is that Satan is a very skillful observer of men, and that by watching men he has a fairly good read of their predispositions and weaknesses, not unlike the skills of a con man, who appeals to the greed of the victim, and tells his victims just what they wish to hear. He also can hear what we say, and that certainly tells him a good deal.

In short, Satan is a powerful foe, much more powerful than mere men, but he is not all powerful, nor all knowing.