COOK spaghetti as directed on package. Meanwhile, heat dressing in large skillet on medium-high heat. Add shrimp and ginger; cook 4 to 5 min. or just until shrimp turn pink, stirring frequently. Add peas and peppers; cook 2 to 3 min. or until crisp-tender.
SPOON shrimp mixture to one side of skillet. Add soy sauce and peanut butter to other side of skillet; cook until peanut butter is completely melted and mixture is well blended, stirring frequently. Mix with shrimp mixture until evenly coated. Sprinkle with onions and sesame seed.
DRAIN spaghetti. Serve topped with shrimp mixture.