Coconut sauce: In a bowl, whisk together all the ingredients. Set aside.
Stir-fry: In a large bowl, pour boiling water over the vermicelli and soak for about 5 minutes. Rinse with cold water and drain well. Set aside.
Pat the scallops dry with paper towels.
Heat half the peanut oil in a wok over high heat. Brown half the scallops, about 1 minute per side. Season with salt and set aside. Repeat with the remaining oil and scallops. Set aside.
In the same wok over medium-high heat, stir-fry the onions, carrots and garlic in the sesame oil, 3 to 4 minutes. Add the coconut sauce. Bring to a boil and reduce until the sauce thickens, 2 to 3 minutes. Add the scallops and cook just long enough to heat through.
Serve on the vermicelli. Garnish with green onions, peanuts and cilantro.