Preheat oven to 200°C/180°C fan forced. Tie drumsticks together with kitchen string. Place chicken in a large baking dish. Whisk marmalade, orange juice, 2 tablespoons of the kecap manis, half the garlic, the ginger and five spice in a bowl. Brush half the marmalade mixture over chicken. Cover loosely with foil and roast in oven for 1 hour 45 minutes.
Remove foil from chicken and bake for a further 30 minutes, or until golden brown and cooked through (juices run clear when tested with a skewer), brushing occasionally with remaining marmalade mixture. Remove from oven and rest chicken for 5 minutes.
Heat a wok over medium-high heat. Add sesame oil and swirl to coat. Add bok choy, chilli, remaining kecap manis and garlic. Stir-fry for 1 minute or until bok choy wilts. Season with salt.
Serve chicken with chilli bok choy and scatter chicken with sesame seeds.