Question

"what are you thinking about? " change into indirect speech ​

Answer 1

what he is thinking about

Answer 2

He was enquired that what he was thinking about.

In this converted indirect speech the whole situation has been conveyed and that makes the sentence meaning and grammatically correct.

The subject verb agreement is well maintained in the sentence as well as the consistency of the tense is properly maintained.

It is changed from the direct speech to indirect speech.