Pat the chicken dry and cut it into roughly 1-inch bite-size pieces.
Combine the coconut milk, chicken broth, soy sauce, brown sugar, and salt in a medium bowl until smooth.
Heat the oil in a large skillet over medium-high heat. Cook the chicken for 3 to 4 minutes on the first side and about 2 minutes on the second. Transfer it to a plate.
Reduce the heat to medium. Cook the onion for 4 to 5 minutes, stirring occasionally, until soft and lightly golden.
Add the garlic, ginger, and red curry paste. Stir constantly for 45 to 60 seconds, until fragrant.
Pour the coconut milk mixture into the skillet. Stir along the bottom of the pan and bring it to a gentle simmer.
Return the chicken and any juices to the skillet. Simmer for 6 to 8 minutes, until the thickest pieces reach 165°F (74°C).
Prepare the rice noodles according to the package directions, usually about 4 to 6 minutes. Drain as soon as they are tender.
Add the drained noodles to the curry. Toss gently for 1 to 2 minutes until coated. Add 1 to 3 tablespoons extra chicken broth if the sauce feels too thick.
Turn off the heat and stir in the lime juice. Taste and adjust the salt or lime as needed. Serve with cilantro or green onion and lime wedges.
