Heat oil in a large pot over medium meat. Add onion and garlic, cook for 2 minutes. Add celery and carrots, cook for 5 minutes until softened, don't let them brown.
Turn heat up to medium high. Gently pour 1.2l of broth, homemade or store-bought. Top up with water if you so desire.
Add thyme, bay leaf and pepper. Stir.
When it starts bubbling, add a little salt to taste. Stir gently and then remove from heat.
For meal prep: Add the bee hoon, top it off with the chicken and then store the soup separately.
To serve immediately: Add the bee hoon, top it off with the chicken and pour the broth in and sprinkle fresh coriander! Enjoy!