For an initial orientation on your topic, you can start looking for information in:
To assess whether a topic is suitable for a thesis, start searching (online) reference works such as:
These reference works provide an overview of the perspectives and scientific discussions surrounding a topic. You will find the basic principles and generally accepted knowledge in a particular field, definitions of jargon, references to basic literature and description of intersections with other fields.
Once you have decided on a subject, you can formulate a problem statement, or research question.