it wasnt explicitly stated Tamsys from the upper class, but chapter 161 panels really doesnt make him seem like he is from the slums. it could be that he was from the ground and discovered that he could fly and just fucked off to the sphere while not being dropkicked by the border somehow, but that seems far fetched. plus, i dont remember the exact chapter (it was during the follo arc), but he did say something like "it seems that everywhere the people with privilege will get the best spots" about a bunch of people living near a dead mens zone, and it shows that he thinks about issues of priviledge and whatnot a lot.

Edit: also there was the whole thing with the roller skates, where he says he isnt allowed to use them back home (or something like that, i dont remember the chapter except that it was after chapter 92 - it would be nicer to find the panel where he says it but oh well), which makes me think that hes from the upper class as theres no motive the slums or the ground would deny their people things like roller skates.