Place first 12 ingredients in an electric slow cooker. Cover and cook on high 7 hours or until chicken is done. Discard lemongrass; stir in cilantro.
Place 1/2 cup of rice and 2 chicken thighs into each of 4 large bowls. Ladle 1 3/4 cups broth mixture over each serving; sprinkle with 2 tablespoons green onions. Serve with lime wedges.