Litalino chown the files and directories to the web user, I assume that's khatvongsongvn. And stop interacting with your installation as root; if you use ssh:
sudo chown -R khatvongsongvn:khatvongsongvn /home/khatvongsong.vn/public_html/storage`
running composer commands should use:
sudo -u khatvongsongvn composer ...
Your cron must be registered under the khatvongsongvn user:
sudo crontab -u khatvongsongvn
(make sure to remove the one for root)
