As you can probably imagine the answer to this question is no a guinea pig can not safely eat fries at all.
More Detailed Answer
To get into a bit more details of why guinea pigs cannot eat fries it is because this food is a heavily processed food.
Processed foods are not good for people in the first place let alone guinea pigs.
Fries have way too much salt on them for guinea pigs to digest so it will make them sick. It can give them digestive issues, weight issues and possibly cause them throw up.
Also another possibility is that too much fries can even cause death for a guinea pig.
Therefore it is important never to give french fries to your guinea pig because it is extremely bad for their health.