Combine shrimp with remaining ingredients including lemongrass, shallots, garlic, ginger, soy sauce, fish sauce, brown sugar, oil, black pepper, red chili flakes, turmeric, and lime juice. Let sit for 30 minutes.
Heat a large saute pan over high heat. Remove shrimp from marinade and cook until pink and firm. Remove from heat and keep warm.
Meanwhile, make sauce for noodles. Melt butter in a large saucepan over medium heat. Add garlic and chopped scallions and saute until fragrant but not browned. Add soy sauce, fish sauce, oyster sauce, and sugar, stirring to combine. Remove from heat and set aside.
Cook pasta according to directions on package. Drain, reserving ¼ cup of pasta water.
Return the pan with noodle sauce back to heat. Add cooked noodles and reserved pasta water, stirring until well combined. Season pasta with salt and pepper. Portion noodles into bowls and top with Thai shrimp, a generous sprinkle of breadcrumbs, and chopped cilantro. Squeeze lime juice on top and serve immediately.
Notes
The marinade for the shrimp can be prepared the day before.