Difficulty in Selecting Thesis Topic

I am a graduate student. I have a 6 credit thesis and I am interested in the field of longitudinal and Bayesian. My supervisor said me to choose my topic. But I am not understanding if I choose a topic how can I know what is the scope (further extension) of this topic because I can't only reproduce a paper in my thesis. I need to know what I am going to do ? If I have a goal I can do a systematic literature review according to my goal.

I am studying longitudinal analysis, Bayesian statistics both in my graduate level.

Could you please suggest me a topic in longitudinal study by showing me the area of extension of the topic ?

Thank you.