Heat the vegetable oil in a skillet over medium heat. Add the red curry paste and stir-fry, then add 3/4 cup coconut milk (about 180 ml) and cook until the curry paste and coconut milk are well combined and the oil separates.

Add the sliced catfish and stir gently. After a few minutes, transfer everything to a larger pot. Place the pot over heat and add the remaining coconut milk and water.

Season with sugar, salt, and fish sauce. Add the fingerroot, pea eggplants, sliced chili peppers, and Thai basil. Bring to a boil, then remove from heat. Serve immediately with hot steamed rice.