Heat the oil in a large saucepan, add the pork and cook, stirring, for 3–4 minutes until browned all over. Add the curry paste and cook, stirring, for 1 minute until fragrant.
Add the coconut milk, stir and reduce the heat to a gentle simmer. Cook for 10 minutes, then add the beans and water chestnuts. Cook for a further 3 minutes.
Remove from the heat, add lime juice to taste and stir through the coriander. Serve immediately with boiled rice.