A Bachelor's thesis or Master's thesis can be started anytime.
Regarding topics for Bachelor's theses, projects, or Master's theses, if you are interested in working, e.g., on
- Boolean satisfiability (SAT) or answer set programming (ASP),
- declarative problem solving (e.g., solving problems using SAT or ASP),
- efficient algorithms for challenging (NP-hard) problems,
- logic & computation, logical languages,
- knowledge representation & reasoning,
- computational complexity of reasoning,
- non-monotonic reasoning, or
- preferential reasoning and computational social choice,
you can contact Johannes P. Wallner for more information for student topics at Graz University of Technology. You can also have a look at the group's webpage and recent publications (see links on the right side), to get a feeling on potential topics.
A thesis can be oriented more theoretically, or more on the implementation side. The concrete topic is discussed with the supervisor.