Shekar - it depends on context. Your PhD thesis is (one assumes) your own work and you can't plagiarise your own work. However, it could be viewed as poor practice to directly cut-and-paste large sections from your thesis. Best to use a plagiarism software to check the matching report - and paraphrase where there is multiple direct copy.
PhD thesis draft should have less than 19% plagiarism for graduation, if you publish article from your thesis, then you need to check your thesis plagiarism and decrease it again.
Sorry , I had to delete my previous comment due to a spelling error.Yes, it is a form of plagiarism.You must observe citation rules even when quoting from your own work.
Plagiarism in any form, even self-plagiarism, is looked down upon all over the world. Instead of exactly copying your work, you need to re-write using different wordings keeping the meaning same if you want to.