Self-plagiarism: Copy part of thesis for blog posts?
You should do two things:
1) Discuss this with your advisor. He/she will know the regulations better than we do.
2) Make it clear on the blog that you the blog-writer and you the thesis-writer are the same person, e.g. by using your real name.

Another issue, that you didn't yet consider but that surely needs consideration is the copyright for your thesis. At some universities, the department/university library wants at least some rights on your thesis. If they then find parts of said thesis copied verbatim to an online platform, you might get into trouble. It might well be that this is not the case at your university or that they don't care as long as you cite your thesis, but this is something you need to clarify before posting stuff.