This could be a variety of issues.
It might be ringworm which you can read about here
http://www.marvistavet.com/html/body_ringworm.html
Another possibility is this could be from a tick carried disease such as Lyme disease or Rocky Mountain Spotted fever.
Your vet can test for tick carried diseases.
You can read about tick diseases here
http://www.mirage-samoyeds.com/tick.htm
And depending on where you live those red abdominal spots this time of year can be due to black fly or deer fly bites. These annoying biting insects bite where the skin is exposed. Their bites leave a red mark on a dog's skin like a drop of blood staining the skin. The marks are most commonly seen on the abdomen or in areas where there is less fur.
Another possibility is mange mite infection. Usually when seen along the abdomen its contagious mange or sarcoptic mange and you can read about this here
http://www.marvistavet.com/html/body_sarcoptic_mange.html
but it might be non contagious or demodectic mange too
http://www.marvistavet.com/html/body_demodectic_mange.html
And if these spots look more like bruising sometimes a problem with blood clotting will show as that along the abdomen. If the dog might have gotten into a toxin or a rodent bait that could be the issue too.
Your best choice may be to have a vet look at the dog and determine just what is going on to figure out just what treatment is needed.
Hope this helps you!