Singapore was part of the British Empire. It was once administered by the British from Calcutta (Kolkata). Many of our laws, including the Penal Code, were imported from India. The Indian Penal Code, in Section 377, criminalises "carnal intercourse against the order of nature". Sodomy was considered a crime under Section 377.
Section 377A of the Singapore Penal Code makes it a crime for two consenting male adults to have sex with each other in private. It does not penalise sex between two consenting female adults. The first question is whether Section 377A should be repealed. The second question is whether 377A is consistent with our Constitution.