Cook spaghetti in a large pot of salted boiling water. Whisk together peanut butter, soy sauce, sesame oil, chili garlic paste, ginger, garlic, and sugar. Thin with the water. When noodles are done, drain and rinse under cold water. Toss sauce with pasta, and thin with more water if needed. Serve topped with a salad of shredded bok choy and carrots dressed with soy sauce, rice vinegar, and a little toasted sesame oil. Season with salt.