BSc: double thesis or thesis with multiple topics? I have been working on two research projects at different departments during my BSc. One of them yielded a conference paper and the other one was initially decided to be my final thesis topic. The latter one is also going well and we are planning to make a journal publication on it. I have to write my final thesis next semester and I am wondering whether I should make two separate theses for two research topics or involve them inside a single thesis. 

I appreciate your opinion!
If you can make one good story about the combination of the two, that's what could make your thesis outstanding. But it's also going to be a lot more work, and if it doesn't work out, you just wasted a lot of time.

If you're not convinced you can and really want to pull this, go and ditch one of the two subjects. It's a lot less hassle for both you and your prof, you'll get a good grade, and that's it.

As was mentioned in the comments, it's already published, so there is no need to publish it again, and in a thesis, which so few people will read ever again.