Heat the avocado oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until it is browned and no longer pink, about 6 minutes.
Stir in the minced garlic, grated ginger, and chopped Thai chilies. Cook for 1 minute until the garlic is fragrant.
Pour in the fish sauce and lime juice. Stir everything together and let it simmer for another minute so the flavors combine.
Remove the skillet from the heat. Spoon the beef mixture into the prepared lettuce leaves and top each cup with cilantro, mint, and sliced green onions.