Preheat the oven to 375 degrees F (190 degrees C). Season both sides of the chicken thighs with salt and pepper; transfer to a baking dish. Bake in the preheated oven, uncovered, for 15 minutes. Mix apricot jam, ketchup, onion, barbecue sauce, and soy sauce together. Pour over chicken thighs. Continue baking until chicken is no longer pink in the center, about 20 minutes more.