How to remove your Singapore Airlines account
Your account will be removed automatically after not having used it for a certain amount of months, as can be read: https://www.singaporeair.com/categoryListing.form?searchBy=SubCategory&subCategory=6675#faq6652
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for Singapore Airlines using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Singapore Airlines. Click here to find out how.