Preheat oven to 400 degrees.
Combine ground chicken, white parts of scallions, lemongrass paste, cilantro, 1 tbsp. fish sauce, garlic, ginger, red pepper flake, panko breadcrumbs, and pinch of salt in bowl. Mix together with hands until just combined, but ingredients evenly distributed. Form into meatballs.
Heat oven-safe skillet on medium-high heat and pour in light oil. Sear meatballs on all sides until brown all over.
Pour in coconut milk into pan to deglaze pan. Stir sauce around, scraping up bits off bottom of pan as you stir. Place oven-safe pan of meatballs into oven and bake for 10 min.
Meanwhile, mix together sliced cucumber and shredded carrots in a bowl. In a separate bowl, whisk together rice vinegar, lime juice, honey, ½ teaspoon fish sauce, and 1-2 pinches of salt. Pour sauce over top of vegetables and mix well. Allow to sit while meatballs finish. Salad can be prepared night before and sit overnight in refrigerator.
Remove meatballs from oven. Serve immediately on top of whole grain rice (optional) with salad. Garnish with green parts of scallions or additional cilantro (optional).