1In large stockpot over medium-high heat, sauté chicken in oil, 3 to 4 minutes.
Add onion and carrots; cook, stirring occasionally, until vegetables begin to soften, about 2 minutes.
Add garlic and cook until fragrant, about 30 seconds.
Stir in tomatoes, bay leaf, and thyme; cook until fragrant, about 30 seconds.
Stir in lentils, salt, and pepper; cover, reduce heat to low, and cook until vegetables are softened, 8 to 10 minutes.
Uncover, increase heat to high, add chicken broth; bring to boil, cover, and reduce heat to low. Simmer until lentils are tender, 40 to 45 minutes;remove bay leaf.
Transfer 3 cups of soup to a blender and puree until smooth. Return pureed soup to pot; stir in vinegar and heat soup over medium-low until hot, about 5 minutes. Stir in parsley.