Cook the pasta per package directions until al dente.
While pasta is cooking, rinse scallops and pat dry. Heat 1 tbsp olive oil and 1 tbsp butter over high heat in a skillet until foamy. Sprinkle scallops with a little salt and pepper; place in skillet in single layer. Cook, turning once, until brown on outside and just opaque in center, about 2 minutes per side. Remove from pan and set aside.
Drain pasta and return to the pot over low heat. Stir in lemon zest, juice, remaining 3 tbsp olive oil, peas, and thyme. Toss to coat, then season with salt and lots of pepper. Add the ricotta and mix gently until pasta is coated evenly.
To serve, divide the pasta between four plates, topping each with three scallops and a sprig of fresh thyme.