Convenience stores and street vendors usually sell the popcorn pre-packaged. You can find bags the size of large pillowcases for sale.
At first I thought that the vendors popped the corn themselves. Now I'm not sure since all the popcorn packaging looks the same.
The twist tie is the only safety precaution. In the U.S. one would not find popcorn packaged in this way. It would only be a matter of time before someone dumped staples or poison into one of the bags!