Singapore passport holders can visit China without a visa for up to 15 days, visit Hong Kong for up to 90 days and visit Macau for up to 30 days. So you don't need a visa for your holiday within the specified duration. As I know, the Chinese temporary travel document is only used for returning home country under emergencies, such as you lost your passport in other countries. I'm not clear about the policy of Singapore Temporary travel docuemnt