This is how Tham works in top:
Did you happen to get filled top? yes.
Is the opponent picking a melee? yes.
Do you know the match-up? no.
Congrats, you can pick Tham and make the lane uninteractive for your opponent and just wait if your team wins by themselves.
Did you won the lane? yes. Congrats. Thats it, you can't actually push.
Did you won the lane? no. Congrats. That's it, just slow down any melee trying to split, they can't dive you anyway.
You have no tp? fear not! use your ult.
You want to permaslow and invalidate your opponent's dashes? fear not! buy iceborn gauntlet and hit your fast af Q!
He is only fun if your heart is pure rocks and spines and you actually don't care about either win or lose. That's tham.
For the kids reading: it's like Snorlax just sleeping in the middle of the road.