Place the Thai chili pepper, garlic, shallot, lemongrass paste, minced ginger, scallions, and lime juice in a food processor. Pulse until finely minced and transfer to a large bowl.
Add the ground pork, fish sauce, brown sugar, and egg and mix with your hands until combined. Season all over with salt. Add the panko and mix with your hands. Add more panko in ¼-cup increments if the mixture is too loose. The mixture should be workable but not too dry. Be careful not to add too much more than ¾ cup panko total.
If you like, fry or microwave a small piece of the mixture until cooked through. Taste and adjust the seasonings to your preference.
Roll the mixture into tablespoon-sized meatballs and transfer to a plate.
In a wide pot, heat 1 tablespoon neutral oil over medium heat. Once hot, add the meatballs in an even layer and cook for 3–5 minutes per side until browned all over. They do not need to be cooked through. Transfer to a plate and set aside.