Heat oil in a medium frying pan over medium-high heat. Add green onions and cook, stirring, for 1 minute. Add garlic and chicken and cook, stirring to break up mince with a wooden spoon, for 3-4 minutes or until mince turns white.
Add celery and carrots to pan and cook, stirring often, for 2 minutes. Stir in kecap manis or soy sauce and toss to combine. Remove from heat and set aside to cool slightly. Serve chicken mixture with lettuce leaves and crispy noodles.