This verse refers to the humiliation of the nobility of Judah by the army of Babylon after the fall of Jerusalem. Were these princes, or nobles, executed and then hung up by their hands as a public example? Or were they tied and hung up by the hands as a form of torture? We don’t know.
What we do know is that the bodies of kings and their sons were sometimes displayed by enemies as a way to celebrate victory and to humiliate and degrade the dead. After the Philistines killed King Saul and his three sons, they hung their bodies on the wall of the city of Beth-shan (1 Samuel 31:8-12).
LAMENTATIONS 5:12 – Princes are hanged up by their hand.