“Thank You, M’am” is a short story by Langston Hughes that looks at how a middle-aged woman treats a young boy who has just attempted to steal from her.
To answer your question , we first need to determine the theme to the story. While there is never just one right answer to this, we can say that the theme in this case is something along the lines of “showing kindness to someone who does not deserve or expect it can have a powerfully positive effect on their life.”
Hughes emphasizes the theme with his characterization of the story’s protagonist, Mrs. Jones. When the boy, Roger, attempts to steal her pocketbook, she turns out to be more than he can handle. She apprehends him and brings him home. Mrs. Jones, however, turns out to be an exceptionally good person. Instead of calling the police or punishing Roger, she cooks for him and then gives him the ten dollars he hoped to steal from her. Her characteristic of generosity leaves the boy stunned. We can assume that it changed him in a positive manner.
We can also cite the situational irony in the fact that she gives money to someone who tried to rob her. Irony is the occurrence of something unexpected. What could be more unexpected than that?
Look at the Enotes link below for some other thoughts on theme in this story.