What is the standard for minimizing the 'awrah of a man when wearing a T-shirt or trousers, especially in a sitting position?

A man must cover his 'awrah, which is the area between the navel and the knee, except from his wife and his bondmaid. Several Prophetic hadiths indicate this. A condition for this covering is that the garment must be thick, not revealing the size of the 'awrah, nor showing the color of the skin. As for wide trousers that do not reveal the 'awrah, there is no harm in wearing them.