Mix together the lime juice, soy sauce and fish sauce in a bowl. Add the prawns and toss together, then set aside to marinate for a few minutes.
Meanwhile, put the noodles in a large heatproof bowl. Pour over boiling water to cover, add 1 teaspoon of the vegetable oil and stir gently. Soak for 4 minutes, then drain thoroughly.
Lift the prawns out of the marinade and pat dry with paper towel. Stir the curry paste into the marinade and set aside. Heat a wok or heavy-based frying pan until very hot, then add 1 teaspoon of the vegetable oil and the sesame oil and swirl to coat the pan. Add the prawns and stir-fry for about 2 minutes until they have turned pink. Remove with a slotted spoon, leaving any remaining oil behind.
Add the rest of the oil to the pan. Toss in the corn and stir-fry for about 30 seconds. Add the bean sprouts and pak choy and stir-fry for a minute, then add the curry paste mixture. Cook for a few seconds, stirring all the time, then add the water chestnuts and drained noodles. Continue to stir-fry for a further 1 minute.
Return the prawns to the wok and pour in the coconut milk. Toss everything together over a high heat until bubbling. Serve immediately, with lime wedges to squeeze over.