I have no idea why SingTel choose to release the news after office hours. I just stepped out of the office when I received this news!!
You can now register your interest for iPhone 4 with SingTel at http://singtelshop.com/iphone4.
The site is in Flash but when you viewed it on your iPhone, it will redirect you to an iPhone friendly page for pre-registration.
Official Website: SingTel’s iPhone 4