As a former (non-native) resident of Singapore, that's one of those features of the local lingo that makes me shudder every time I see it, but it's probably already crossed the line from "mistake" to "accepted local evolution". It certainly is well entrenched, as I've seen it in bank letters about choosing good passwords, and it's in this university policy as well:
Have both upper and lower case alphabets
http://iits.smu.edu.sg/cyber-security/password-management
Quite a few other telltale Singlish features in there as well, eg. the use of "staff" to refer to a single employee and using "credential" instead of "credentials". Both of these are rooted in how Chinese and Malay lack a grammatical plural.