Cut the skinless chicken thighs into equal, bite-sized pieces. Break the whole cauliflower into florets and grate them coarsely with a box grater or food processor into fine cauliflower rice. Cut the bok choy into thick strips and rinse them clean. Roughly chop the fresh cilantro and set aside.
Place a large pan on the heat and briefly sear the chicken pieces on all sides. Add the red curry paste and cook for one minute to release the flavors well. Deglaze with the coconut milk and add the lime leaf to the sauce. Turn the heat down and let the chicken simmer gently for about fifteen minutes until cooked through.
Steam the grated cauliflower rice in a steamer basket or colander over boiling water for about five minutes until tender-crisp. Add the sliced bok choy to the steamer in the last two minutes so the leaves just wilt slightly but the stems stay crispy. Meanwhile, stir a splash of fish sauce through the simmering curry to season it well and remove the lime leaf.
Divide the warm, steamed cauliflower rice among plates. Spoon the chicken thighs with the red coconut curry over the rice or place alongside. Add the steamed bok choy to the plate and scatter the roughly chopped cilantro over everything.