In a mixing bowl, combine curry powder, garlic powder, paprika, turmeric, salt, pepper, and a drizzle of oil to form a fragrant marinade. Toss in boneless chicken thighs, ensuring each piece is generously coated. Let the chicken sit for about 10 minutes.

Heat a large skillet over medium heat and add a splash of oil. Once the oil shimmers, add the marinated chicken thighs to the pan. Sear them for approximately 5 to 6 minutes until golden brown and cooked through, reaching an internal temperature of 165°F. Remove the chicken from the skillet and set aside temporarily.

In the same skillet, add the chopped onion and minced garlic, stirring continuously for 2 to 3 minutes until softened and fragrant.

Stir in the red curry paste, allowing it to coat the onions and garlic evenly. Cook for about 1 minute until fragrant.

Pour in the creamy coconut milk, stirring slowly as it combines. Bring to a gentle simmer over medium heat for around 2 to 3 minutes.

Add the udon noodles and the cooked chicken to the simmering sauce. Stir gently and continue to simmer for an additional 2 to 3 minutes until noodles are tender.

Taste and adjust seasoning as desired, then plate the dish and top with cilantro, lime juice, and chili flakes.