Having said all that - if some earlier POD produces butterflies which include additional training for the Imperial defenders, let alone additional planes (because they aren't being expended in the Med and North Africa or sent Lend-Lease to the USSR) or tanks (Japanese WWII armor is often ridiculed, but they brought 200 to Malaya and the defenders had none) or antitank ammunition (the 2-pdr ammunition had problems with the Malayan climate and lost effectiveness with prolonged storage), then the Japanese advance will stall before Singapore surrenders and have to wait for at least additional supplies to be delivered to Yamashita, if not additional troops.
However, that assumes that the IJA wouldn't amend their plans accordingly, which would be surprising.