OnePlus 5Ts sold in mainland China do not have Google Play on them. So you'd either have to import one from somewhere else, like Hong Kong SAR, or see if a PRC version 5T can have it's firmware flashed to the international versions, which do have Google Play, etc. I don't know anything about the latter myself.
FYI Chinese version PlusPlus phones have something called HydrogenOS, while international ones have OxygenOS. One has Google Mobile Services(GMS), and the other doesn't, and there are other differences between them as well.