Can my PhD thesis supervisor be a reviewer for my paper? I want to know whether my PhD thesis supervisor (with whom I have co-authored many papers) is allowed to be a reviewer for one of my journal submissions?
In many cases this would be inappropriate. PhD advisors are considered to have a permanent conflict-of-interest when it comes to their advisees. 

Some conferences/journals relax this condition and allow for reviews from former collaborators if there has been no collaboration in the past 5-6 years (or some similar time window). You should check the rules around CoI for the particular journal if these are publicly available.

However: it is best to not have your PhD advisor listed as a potential reviewer. If the Associate Editor or Editor-in-Chief makes that call -- to have an advisor review the advisee's work -- it is a different matter but one should not rely on obtaining reviews from former advisors.