If you are writing a thematic paper on The Kite Runner's portrayal of truth, you might consider using Baba statement about theft and the truth. In Chapter 3, while explaining sin to Amir, Baba says,
"When you tell a lie, you steal someone's right to the truth" (18).
If you use this idea in your thesis statement, you can discuss the various times in the novel that truth was "stolen" from characters (from Amir, from Hassan, from Sohrab), or you can write about hypocrisy which is also a form of hiding truth from others. For example, along with the statement above regarding truth, Baba also tells Amir that it is "better to get hurt by the truth than comforted by a lie." This is another premise that you could present in your thesis. Just remember to limit your thesis to one sentence and to make it meaningful statement, not a question.