The Awra for a man is technically just the private parts. However, a couple of points to consider:
1- When praying, we must be clothed appropriately to show respect for God. Men can technically pray in shorts, but it’s Makrouh (not recommended). Their prayer is also valid if they are shirtless, but it’s not recommended.
2- When men are in the presence of non-mahram women, they must be dressed appropriately. Dressing provocatively is haram.