Travellers and bona fide crew members are entitled to duty-free concession for liquors if all the following conditions are met:

You are 18 years old or above;
You have spent 48 hours or more outside Singapore immediately before arrival;
You are not arriving from Malaysia;
The liquor is for your own consumption; and
The liquor is not prohibited from import into Singapore.


https://www.customs.gov.sg/individuals/going-through-customs/arrivals/duty-free-concession-and-gst-relief/#:~:text=There%20is%20no%20duty%2Dfree,would%20be%20required%20for%20clearance.