While these hangers are officially accepted in the recycling bins in Singapore, most plastic hangers are made from non-recyclable plastic (#6 polystyrene and #7 polycarbonate) so they will get removed during the recycling sorting process and eventually end up incinerated.  

Do the system a favor and just put it directly in the trash yourself.

The biggest source of surplus plastic hangers is from dry cleaners (most clothes stores keep their hangers after a sale).