Existing hypothesis, same country, but different years and setting – is it plagiarism?
Plagiarism is selling somebody else’s idea as your own. Therefore as long as you properly cite the other paper, you are in no danger of committing plagiarism. The worst that can happen is that you are reproducing an existing study¹ instead of doing something novel. Whether this is a problem, is for you and your supervisor to decide, as you know the differences in detail.

On top, suppose you hadn’t found out about the other study: In this case you would not have committed plagiarism since you cannot possibly use the ideas of others without knowing them. Had you published your paper in this case, you would perhaps² be guilty of sloppy literature research, but not of plagiarism. However, the evidence may (incorrectly) point to you being a plagiarist and thus you still want to avoid this situation.




¹ which scientists almost universally agree on being done too rarely.
² if the other paper is sufficiently easy to find