In a large skillet or wok, stir-fry the red curry paste in cooking oil over low heat for 30 seconds. Add the thinly sliced beef to the skillet. Cook and stir over medium-high heat for 2 minutes or until the meat is browned. Stir in the fish sauce, sugar, and salt.
Add coconut milk; stir until the mixture is well combined. Add water and lemon grass. Cover and simmer for 20 minutes.
Add eggplant; cover and cook for 3 minutes. Add long beans. Cover and cook over medium heat about 5 minutes or until eggplant and beans are tender.
Stir in the Thai basil leaves. Serve with hot cooked rice. Makes 4 servings.
You can substitute green beans for the long beans in this recipe. Just precook the green beans in boiling water about 5 minutes before adding them to the recipe after the eggplant, instead of the long beans.