This may very well be that your teacher has a set of vocabulary that he/she wants you to know that is not necessarily a mainstream set. If I were to take each of those terms, I would believe thematic topic means that you should pick a topic that stays on a theme in the story. For example, habits of society or traditions are thematic topics. Children's games could also be a topic, but it doesn't necessarily centralize on a theme in this story.
A thematic statement would likely take a stance about that thematic topic. For example, you could say: Shirley Jackson's short story "The Lottery" depicts the evil that can be the overused traditions of any society. This thematic statement might make for a nice thesis statement.
I agree with the above, and would add, that a thematic topic can be turned into a thematic statement by following a fairly simple step-by-step process.
Typically, when writing an essay about a theme of a story, you begin with a basic thematic topic. Think of this as a subject of the short story. If you were to use the example above (societal traditions), the procedure of turning a thematic topic into a thematic statement is as follows:
- Ask: What are the causes of societal traditions or what are the effects of societal traditions in the story?
- Brainstorm a list of answers to the questions above.
- Use the list of plot details to then answer: Through events in the story, what is the author trying to say about societal traditions?
- You will find that you might have to make this question more specific as you look at your brainstormed list. In this case, the author is clearly talking about a negative (or evil) societal tradition, so you could re-write the question to say "What is the author trying to say about evil societal traditions?"
- Do not use any of your examples in the one sentence answer to #4, but instead, write a general answer that will be backed up (or proven) by examples. Notice how the example from above does exactly this (and could be proven with examples from the text which you would have already generated in step #2):
Shirley Jackson's short story "The Lottery" depicts the evil [side of] overused traditions of any society.
At this point, I always encourage students to think about revising the original statement to make it even stronger. I might tweak the above thematic statement to make it more argumentative:
Shirley Jackson's short story, "The Lottery," shows that unquestioned tradition combined with ignorance results in people turning a blind eye to habits which are inherently evil.