Bring water to boil in a large pot, cook spaghetti noodles accordingly to package instructions.
While noodles cook, heat a large skillet with cooking oil under medium heat. Pat dry defrosted shrimp and sear shrimp for a few minutes on each side until shrimp is fully cooked (turn pink/orange, and curls). Avoid overlapping shrimp when searing - cook in two batches if needed. When shrimp is cooked, remove shrimp promptly from skillet.
Add butter to skillet, followed by minced garlic, fish sauce, oyster sauce, brown sugar, and sesame oil. Stir to combine.
Add 1/4 cup of pasta water to garlic sauce. Stir to combine. Remove skillet from heat.
Drain pasta and add pasta to sauce. Toss pasta in sauce.
Add shrimp, and toss pasta and shrimp in sauce.
Garnish with green onions. Serve and enjoy!