There is no need to so imagine oneself as witness of the thoughts. It is best to remain as one’s Self.

Devotee:  “Can one imagine oneself as witness of the thoughts?”

Ramana Maharishi:  It is not the natural state. It is only an idea (bhavana) - an aid to stilling the mind. The Self is ever the witness, whether so imagined or not. There is no need to so imagine except for that purpose. But it is best to remain as one’s Self.