Answer:
The devil does not know our thoughts, only God searches the thoughts and heart of man.
I do believe we should “watch our tongues” as the Bible tells us to because anything spoken can be heard by others, so I would also assume the evil forces lurking out there would be able to hear also. That is why anything we confess with our mouth should not be accusatory or negative but rather all things should be focused on living a Godly life and example to others.
Jude 1:9 Yet Michael the archangel, when contending with the devil he disputed about the body of Moses, durst not bring against him a railing accusation, but said, The Lord rebuke thee.
Pastor Brad