If you’re very thin, chances are you have what’s known as “skinny-fat syndrome.” Basically, you don’t have a lot of weight on your body, but you lack muscle and have more total body fat mass.
This program will still work for you as you still need to lose the fat covering your abs. After you get a little leaner, I would highly recommend reading the 9 to 5 Abs Muscle Toning Guide. Chances are if you build more muscle mass, you would like the way you look and your abs would “pop” more than they do right now.