In a large bowl, whisk together peanut butter, soy sauce, honey, rice vinegar, sesame oil, garlic, ginger, and red pepper flakes until smooth and well combined.
Add the chicken thighs to the bowl, ensuring they are fully coated with the peanut sauce. Cover and marinate in the refrigerator for at least 30 minutes, or up to 2 hours for more flavor.
Preheat your grill or a large skillet over medium-high heat. If using a skillet, add a little oil to prevent sticking.
Remove the chicken from the marinade (reserve the marinade) and cook for 6-7 minutes on each side, or until the chicken is cooked through and reaches an internal temperature of 165°F.
In a small saucepan, heat the reserved marinade over medium heat until it comes to a simmer. Cook for 3-5 minutes until slightly thickened. Serve the grilled chicken over jasmine rice, drizzled with the thickened sauce, and garnish with green onions and cilantro.