Is it advised to give a suggestion how to cite in the thesis document itself?
I wouldn't include this statement.  Academic authors don't need to be told how to cite theses - they already know.  And I think it does make it sound like you insist on a particular citation style, which may feel awkward to authors who want or are required to use something else.  (I don't see it as "begging for citation", though.)

It is certainly a good idea to include the DOI, but I would just write something like


  Digital Object Identifier:  https://doi.org/10.15420/882.2249


in the colophon or some other convenient place in the document's frontmatter.