Heat 1 tablespoon olive oil in a large stockpot or Dutch oven over medium heat. Add onion, carrots and celery. Cook, stirring occasionally, until tender, about 3-4 minutes.
Stir in garlic, ginger, lemongrass, thyme and rosemary until fragrant, about 1-2 minutes.
Stir in chicken stock, bay leaves and 1 cup water. Add chicken and bring to boil; reduce heat and simmer, covered, until the chicken is cooked through, about 10-12 minutes. Remove chicken and shred, using two forks; set aside.
Stir in pasta and cook until tender, about 8-10 minutes.
Stir in chicken and lemon juice; season with salt and pepper, to taste.
Serve immediately, garnished with chives, if desired.