Is it normal to feel and see abdominal aorta pulse in stomach when laid down slender male?

It can be normal.: The abdominal aorta is a very large blood vessel, and whereas in the chest it is hidden by the sternum/rib cage, in your abdomen it is covered by the intestines and soft internal organs, which vibrate when your blood pulses through the aorta. So yes, if you are thin and there isn't a lot of fat on your abdomen, you will feel/see the faint pulsations of this great blood vessel.