Cook the brown rice in plenty of salted water for about twenty-five minutes until al dente, then drain. The whole-grain bran retains the fiber, causing this rice to raise your blood sugar much more gradually than white rice.
Cut the chicken thigh fillet into bite-sized pieces, the eggplant into two-centimeter cubes, and the green beans into three-centimeter pieces.
Heat the coconut oil in a wok or deep skillet and fry the curry paste for one minute over medium heat until it darkens and becomes highly fragrant. This step is the most important of the entire dish: the aromas in the paste are fat-soluble and are only released when fried in oil.
Pour in one-third of the coconut milk and let it simmer for two minutes until the oil visibly separates. Add the chicken and sear it on all sides. Chicken thigh remains much juicier in a curry than breast meat because the slightly fattier meat does not dry out during longer simmering.
Pour in the remaining coconut milk along with the fish sauce and kaffir lime leaves. Add the eggplant and let everything simmer gently for twelve minutes. Add the green beans for the final five minutes so they remain crisp-tender and bright green. Season to taste with lime juice and finish with Thai basil and sliced red chili. Serve over the rice.