Acceptable documents issued by Singapore
ID card ("NRIC")
Just a link to Wikipedia
An image found with google search is attached to this article.
Note that the ID card does not seem to contain a personal signature. If the photo does not match well you should consider trying to verify the fingerprint...
An image of a driving licence (also found by google) is attached to this article. It satisfies the minimum requirements "government-issued photo ID containing the birthdate", but is not an ideal document. Accept it as single identification only if the photo matches well.