The essay "Prison Studies" appears in Malcolm X's The Autobiography of Malcolm X. The essay details the time Malcolm X spent in prison. During his time in prison, Malcolm X decided to educate himself (enough to make it look like he was a properly and institution educated man). His interest in education (particularly reading, writing, and speaking well) was sparked by another inmate (Bimbi-who Malcolm states made him "envious of his stock of knowledge").
The introduction of Malcolm X's essay contains two sentences, neither which offer a solid thesis statement. In fact, the essay does not seem to offer one singular thesis at all. Instead, the essay offers four. As far as I can gather, Malcolm X desired his readers to identify four very important points within the essay:
1) "No university would ask any student to devour literature as I did when this new world opened to me, of being able to read and understand."
2) "As I see it today, the ability to read awoke inside me some long dormant craving to be mentally alive."
3) "My homemade education gave me, with every additional book that I read, a little bit more sensitivity to the deafness, dumbness, and blindness that was afflicting the black race in America."
4) "In fact, prison enabled me to study far more intensively than I would have if my life had gone differently and I had attended some college."
In the end, one can define the thesis upon his or her own: Malcolm wished readers to know that education is important and can be found (and achieved) in the most unexpected places.