Please see Travel Advisories from the Singapore’s Ministry of Health (MOH) on COVID-19 :
With effect from 19 October 2020, 2359hrs, all travellers who are not Singapore Citizens or Permanent Residents, and who have recent travel history to Indonesia within the last 14 days prior to entry will be required to take a COVID-19 Polymerase Chain Reaction (PCR) test within 72 hours before departure.
Travellers will need to present a valid negative COVID-19 test result as a condition of approval to enter or transfer through Singapore. Travellers from Indonesia entering Singapore will still be required to serve a 14-day SHN at dedicated SHN facilities and to take a negative COVID-19 test before the end of their SHN.
Ferry Operators’ to ensure that the departing travellers (excluding Singapore Citizen and Permanent Residents) have in possession of a COVID-19 PCR negative test certificate, which is taken within 72 hours before departure.
From 26 Oct 2020, Applications for Reciprocal Green Lane (RGL) between Singapore and Indonesia to facilitate essential short-term business and official travel will commence. For procedural requirements, health protocols, and application process : – https://safetravel.ica.gov.sg/indonesia/rgl/requirements-and-process