A Master thesis discusses experimental work carried out on existing data structures and also proposes a few variants. Can this thesis be cited in a paper for comparisons or is it that only a Ph.D thesis be referred in related work?
As far as I know there is no restriction in using a master degree thesis as a reference. If I remember correctly, I have used it myself as well. Moreover, in the following link you can see that a master thesis was shown as a example (APA referencing style):
There should not be any problem in citing a Master thesis as long as you cite it properly, avoiding plagiarism and include it into the reference list. Just be careful to note that whether it is a published or unpublished work.
Master's thesis is carried out for academic requirements, within shorter time span. There the requirement is to find out whether the student has grasped the theory and has applied the learning. Real research orientation happens only at MPhil and further. Even though the project could have been good, the research citations can pick literature review of the process and not the outcome of the project
Rely more on the ethics of research, depends on the data correctness, works which are not reviewed or have limited rights should be refereed but must be cited as required. The thesis must cite the sources, but do not lean on the works to prove own points. No problem for Masters work.