The kingdom of God is within you.
Jesus says first that it doesn’t come by observing it. You can’t see it. You can see crowds around Jesus but you can’t see inside people hearts.
Jesus spoke of two men going to the temple. One goes home no different. The other goes home forgiven. And it’s the tax collector not the priest! But you couldn’t tell as you saw the two men leave the temple.
Jesus had just said that one man of the ten that were cured of leprosy came back to thank him. The man was moved by gratefulness to come back and thank Jesus.
This again shows an internal feeling. It can’t be seen easily. Jesus points it out. He remarks on the act of this one man.
Was that man told to thank Jesus? No. But his heart led him to do it. This is the kingdom of God working within.