Heat vegetable oil in a large stainless steel skillet or wok over medium-high heat until shimmering.

Add ground chicken and cook for 5 to 7 minutes, using a spatula to break the protein into small, uniform crumbles until fully browned.

Incorporate the diced onion, minced garlic, and grated ginger into the skillet and sauté for 3 minutes until the onions are translucent and aromatics are fragrant.

Add the chopped water chestnuts, soy sauce, hoisin sauce, rice wine vinegar, toasted sesame oil, and red pepper flakes to the chicken mixture.

Reduce heat to medium and simmer for 2 to 4 minutes, stirring occasionally, until the sauce has reduced and glazed the chicken thoroughly.

Remove the skillet from heat and fold in the sliced green onions.

In a small emulsion bowl, whisk together the sweet Thai chili sauce, sriracha, fish sauce, and lime juice until the sauce is homogeneous.

Portion the chicken mixture into the center of the prepared butter lettuce leaves.

Serve immediately with the Thai chili sauce drizzled over the top or on the side for dipping.