Generally speaking, in principle, the topic of master's graduation thesis can't be changed at will, because the topic has been audited by the tutor and the school, and changing the topic at will may affect the quality of the thesis and defense.

But if you really need to change the subject, you need to apply to the tutor and the school, and you can change it after approval. The specific process may vary from school to school, and you can consult the educational administration department or tutor of your school.