Combine the lemongrass, soy sauce, fish sauce, lime juice, vegetable oil, ginger, garlic, sugar, and sesame oil together in a large baking dish.
Coat each side of the ribs in the marinade then nestle into the baking dish.
Cover with plastic wrap and refrigerate for 6 hours, flipping them occasionally.
Remove the ribs from the refrigerator 30 minutes prior to cooking.
Heat the grill pan over medium-high heat; coat the pan with cooking spray then, working in batches, sear the ribs until browned, 4-5 minutes per side for medium-rare.
Transfer to a plate and let rest for 5 minutes. Top with sliced green onion and fresh cilantro leaves. Serve and enjoy.