Cook the green beans in a pan of boiling salted water for 3 minutes. Drain and set aside.
Heat the oil in a wok or large frying pan. Add the green curry paste and sugar and cook over a fairly high heat for 1 minute, stirring. Reduce the heat slightly and stir in the chicken pieces and lime leaves, until coated in the paste.
Add the coconut milk and fish sauce and bring to a simmer. Cook gently for 25-30 minutes until thickened slightly. Stir in the green beans, coriander and lime juice.
Garnish with lime wedges and coriander and serve with boiled rice.