Place the soy sauce, brown sugar, lime juice, orange juice, sweet chilli sauce, chilli-garlic sauce, garlic and curry powder in a large plastic zipper bag. Seal and knead the bag with your fingers to mix all the ingredients and dissolve the sugar. Place the chicken thighs into the marinade, squeeze out the air from the bag, zip the bag closed, and refrigerate for 4 hours or overnight.
Preheat an outdoor BBQ for medium-low heat; lightly oil the grate.
Remove the chicken from the bag, pour the excess marinade into a small saucepan, and bring to a full boil for about 1 minute to sterilise the marinade.
Barbecue the chicken thighs until they are no longer pink in the middle, about 25 minutes, basting them generously with the sterilised marinade as they cook.