Warm the oil in a large skillet and add the bok choy. Saute until it's cooked al dente.
Add the shrimp and get them warmed up. (If they were pre frozen, make sure they are well thawed and the liquid has been drained off.)
Stir in the peanut butter, vinegar and garlic powder, stirring until everything is coated in a creamy peanut sauce.
Season with salt to taste.