I'm a Chinese citizen holding US green card, and just submitted my Singapore tourist visa application with air ticket and hotel booking at Singapore consulate in the US. I wonder if I ever make changes to these reservations when I see a lower price available, will such change affect my visa review/approval process, or will it cancel a granted visa?
Singapore asks visa applicants applying in the US for
A copy of air ticket and hotel reservations. Detailed proposed itineraries (flight and hotel) will also be accepted.
If you submitted a proposed itinerary with your application, which is still under review, go ahead and and book. If you provided confirmation for your tickets and hotels, it may be wiser to wait until your visa is issued. After visa issuance, changes which do not significantly alter your itinerary are acceptable.
The Immigration & Checkpoints Authority notes that
A Singapore visa is not an immigration pass. It is a pre-entry permission for the holder of a valid Singapore visa to travel to, and seek entry, into Singapore. The grant of an immigration pass will be determined by the Immigration & Checkpoints Authority (ICA) officers at the point of entry. Possession of a valid visa alone does not guarantee entry into Singapore.
Should you need to, you can reach Singapore's Ministry of Foreign Affairs at firstname.lastname@example.org or at +65 6379 8000.