Places like HKG and SIN can have you descending early on a STAR to make height and speed restrictions. You must follow these requirements unless they are actually removed for you. Many airports have you doing this, but arriving at off-peak times it is likely they will just not give you a STAR. Most major airports do have such restrictions. At HKG, you can follow the very long convoluted arrival, but you are usually aware that short cuts cutting out the extreme routing are the normal order of the day, so you fly your descent planning to do the long routing required, but keeping an eye on fact that you are likely to be cut really short and making sure you are in a position to take advantage of the short cuts that are normall given.