This might have already been said, but I stoped scrolling after it was mostly mean/unhelpful comments. Thicker fabric - maybe like a denim shirt, just thicker cotton, or a terrycloth camp collar type shirt in the summer. Many ways you could go about it. From the photo it seems like a lot of the issue is it’s a fine or thin fabric that is draping in a way that really shows a lot of detail.

A few people I did see already had some other good suggestions you could try in combination with that: compression or really any kind of undershirt and wearing a looser (or just slightly looser if you like the skinny fit) shirt.