The short story Thank You M'am by Langston Hughes is told from an omniscient third person perspective. The narrator sets the scene by describing Mrs. Luella Bates Washington Jones on her route home from work one late evening at around 11 pm. A third person omniscient narrator ensures that this story is placed in its correct context without a need for the reader to form an opinion or make a judgement about the hapless boy, Roger. At first it seems Roger is unlucky because he has been caught but it is revealed that his random encounter with Mrs Jones is the perfect opportunity for Roger to turn his life around.
There are various possible choices for a narrator of a story including the first person narrator who, as the name suggests, tells his or her own story. That would have been too subjective for this story and would have revealed either Roger's own story or Mrs. Jones's story making it an unreliable account of what happened. Using a third person omniscient narrator ensures that the reader can explore the situation as a whole and make an assessment based on all the information. The reader is also able to understand both characters. The relationship which develops between Roger and Mrs. Jones is apparent and their interspersed dialogue contributes to the character development. This relationship is a crucial element of the story and is best told by a third person narrator as it creates an unlikely bond between old and young and leaves the reader with a sense that there are commonalities between the two characters which bodes well for Roger's future and removes any uncertainty.
Here is a video version of Thank You, M'am, to help you understand the story: