Gently toss grapefruit segments and avocado slices in medium bowl. Set aside. Mix vinegar, 1 tablespoon of the olive oil, shallot, 1/2 teaspoon of the thyme, 1/8 teaspoon of the salt and pepper in small bowl with wire whisk until well blended. Set aside.
Mix remaining 1 teaspoon thyme, ginger and remaining 1/4 teaspoon salt in small bowl. Coat scallops evenly on both sides with spice mixture. Heat remaining 1 tablespoon oil in large skillet on medium-high heat. Add scallops; cook 6 to 8 minutes or until scallops are golden brown, turning once.
Divide spinach evenly among 4 serving plates. Top each with scallops and grapefruit mixture. Drizzle each salad with about 1 tablespoon of dressing. Serve immediately.