PAXboy, I was going to point out that the requirement was not one imposed by the airline, but by the country, but started wondering whether that requirement actually exists for transiting passengers, so I did a search and found this:
https://www.mfa.gov.sg/content/mfa/o...n/faq_new.htmlCan I travel with less than six months validity?
You can transit if you do not need to go through immigration in Singapore, though you will still need permission from your airline to board the plane. However, if you do need to go through immigration, you are strongly advised to renew your passport before travelling.
So it looks like you were right after all, you do not need the additional validity for transiting, but at the same time, the airline is able to prevent you from boarding on those grounds.
Fun, eh?