Make the marinade: In a bowl, whisk together Thai curry paste, coconut milk, lime juice, fish sauce (or soy sauce), garlic powder, and a pinch of salt and pepper.
Marinate the fish: Add fish pieces and gently toss to coat evenly. Cover and refrigerate for 15–20 minutes.
Preheat the pan: Heat a skillet or grill pan over medium-high heat. Lightly oil the surface.
Cook the fish: Place fish pieces on the hot pan, leaving space between them. Cook for 2–3 minutes per side, turning gently, until golden and cooked through (opaque and flaky).
Rest and serve: Remove from heat and let rest for 1 minute. Garnish as desired and serve immediately.