There are no retirement visas available to live in Singapore and it is very difficult for people to retire here. In the past, it was possible to apply for a long-term visit pass; however, that visa is now only available to employment pass and S pass holders. One option is for retirees to try and secure an investment visa. However, that requires making a significant investment in Singapore and demonstrable business experience.
You can read more about the investment visa here: http://www.edb.gov.sg/content/dam/edb/en/why%20singapore/entering-singapore/GIP-Global-Investor-Programme-Factsheet-EN.pdf