In a bowl, combine the curry powder, soy sauce, fish sauce, and sugar.
Add the chicken (or beef) pieces and mix well to coat. Let it marinate for at least 30 minutes, or overnight in the refrigerator for better flavor.
Heat vegetable oil in a large pot or Dutch oven over medium heat.
Add the chopped onion and cook until softened, about 3-4 minutes.
Stir in the minced garlic and ginger, and cook for another 2 minutes until fragrant.
Add the marinated meat and cook until browned on all sides.
Sprinkle in the curry powder and turmeric powder, and cook for 1-2 minutes, stirring constantly.
Pour in the coconut milk and chicken or beef broth. Bring to a simmer.
Add the potatoes, carrots, and green beans. Stir well and let the curry simmer for about 20-25 minutes, or until the meat and vegetables are tender.
Stir in the chopped tomato and tamarind paste (if using). Adjust seasoning with additional fish sauce or sugar if needed.
Garnish with fresh chopped cilantro.
Enjoy your meal!