Heat the olive oil in a large pot on medium heat. Add in the diced onion, garlic and ginger and sauté for five minutes until the onion has softened.
Add in the curry paste, stir and let cook for two minutes before stirring in the broth, coconut milk, fish sauce, lime juice and shredded chicken.
Let the broth simmer for five minutes before adding in the zucchini noodles, scallions and half of the sliced red chillies. Let the courgette cook in the broth for one minute before removing from the heat (don't let them overcook and become mushy).
Divide between bowls and top with the remaining slices of red chillies and Thai basil.