I'm not against direct training abs but if you want to see your abs low body fat is what is needed.
Also heavy squats and deads give a decent amount of indirect ab work.
Plenty of skinny blokes have abs without any training at all. Like I said if you can't see you abs you are probably just too fat.
Not all skinny blokes have them...It's genetics too my bf% is pretty low ATM there there but they need direct work. I belive all the inderdct work hence deadlifting and squats have thickened my torso. If I was to get to 6-7 % then they would be clear as day with not much direct training. but I aiming to have them visible at 10%-12% which is very possible. A good point of low bodyfat is tricep fat and chest they are high fat storage spots.