In what part of the book Kaffir does the tone become ironic?
In general, the tone turns ironic towards the end of the book where Mark has succeeded in becoming educated and has also forged links with white tennis clubs in South Africa. He narrates certain situations with an ironic tone. For example, he helps a man from his neighborhood with the bureaucracy and the Afrikaans man is surprised the Mark speaks Afrikaans so well.
There is a great deal of irony in the way Mark Mathabane tells about his mother's belief in religion and the reality of the situation in which they live.
In addition, many of the events which occur in the book are conveyed in an ironic tone. For example in Chapter 24, the people learn about Muhammad Ali and cannot believe that a black man would be allowed to beat a white one. Mark tells about how he inspired by Muhammad Ali decided to be a fighter too only to get beaten up the first time he tried it. His final pronouncement, "To hell with Ali" sums up his belief that he would just have to find another way to get out of Apartheid.