My advisor's new student copied parts of my PhD thesis; advisor doesn't care. What to do?
You have two options:


Not care about plagiarism enough to warrant getting involved. 
Care about plagiarism to the degree you get involved.


There are arguments for both points here. 


It would be an obvious matter of record as to whose thesis was written first if anyone else happened to notice the similarities. Why get involved further? You notified the adviser, let him deal with blowback from letting a student plagiarize. Pushing the issue further would just compromise your relationship with your adviser. Whistleblowers rarely get rewarded properly anyway. And, cynically, some universities may not even care about a student plagiarizing parts of a thesis. It's more paperwork and labor for them to deal with and it's easier to just hope (from an administrative perspective) that the problem goes away.
Based on what you have told us, it seems reasonable that your thesis was plagiarized from. You have contacted the adviser about this and he declined to do much about it. The graduate college and university administration, however, may not concur with your adviser. Plagiarism should be stopped on principle alone. I would report the offending thesis to the graduate college and see if they are willing to investigate it further. If you really wanted to do some nasty damage and the university declines to investigate, notify the local newspaper and see if they'll send over some junior journalist to write a spot on how your university is allowing plagiarism to occur. 


Part of writing a thesis is learning to articulate in your own words what your research is about. This has to do with much more than just shoving original data in a table.   

If your adviser told you the student "might not know what plagiarism is" then.....wow.....No one reaches graduate school and is completely oblivious to what plagiarism is. Let's be honest here. 

For me personally, I would let it go. The network with my adviser is more important to my career right now. This is pragmatism, not principle, speaking.