Thanks to Piter Punk who accepted my suggestion about replacing broken Indonesian mirror sites with a newer one which should work and incorporate the changes in the latest slackpkg tool. Since this tool has been included as a default package (thus supported by default), this will make ease Slackware users in Indonesia to get a faster updates on Slackware once they installed this tool.
FYI: About mirrors in Indonesia, they are updated once a day, usually at midnight (Indonesian time), so updates will be seen by slackpkg at least one day after the announcements of the changes. If you want better and faster updates, consider running rsync service to synchronize the repository on your local computer
Too bad, the mirrors is not copied to the Slackware's website.