I know WWBGD and remember when he got denied boarding in the incident with United Airlines check-in. It's always a gamble when airline staff try to assess your documents that they will refuse to check you in. This is what happened in that situation.
However, I have personally entered Singapore with less than 6 months validity on my passport a couple of times, the last time was in 2009. I'll explain what I did in anticipation of my arrival, but in the end all the extra foot work was wasted. A printout of my hotel bookings and departing ticket was all that was required for Singapore Immigration to stamp me in.
Unneeded legwork:
On a previous trip through Changi airport, I went down and spoke to an Immigration supervisor (on the side counter of the arrivals hall before you cross through immigration. My questions were similar to those stated above, that on a future visit I would be under 6 months validity. They seemed puzzled and unprepared to deal with me or answer questions, but did give me an email address for Singapore Immigration that they promised me would. My emails to them were never acknowledged or replied to. I decided to go anyway.
Arrival:
I did a printout of my hotel booking and ticket onward, flew over, and approached the immigration official as normal. Glancing at my passport, he noticed the short expiry and looked up questioningly. I didn't even wait for his question, jumping in with "I am staying at the XXXX (hotel) and have my ticket home in 3 days! They're here on printouts, if you'd like to see them!"
He thought for about 2 seconds and then just stamped me in. Next in line was his final motion to me.
A non event. Maybe the airlines are worried about protecting themselved, but the country's officials can and will weigh each situation on its own.