Here is in a nutshell what you need to know.
Health Supplements are a really easy product.
At the time when I am writing this little article (March 2018), health supplements can be imported and sold without any license from the Singapore government agencies. The sale of health supplements does explicitly not need any pre-market approval.
However, before importing and selling the respective health supplements in Singapore, it is recommended to verify whether the products comply with the official requirements. There is a very helpful webpage of the Health Sciences Authority (HSA) of Singapore, which also provides specific guidelines for health supplements. The webpage also has a link to an inquiry form that can be used to clarify upcoming questions with HSA.
Please note that the laws in Singapore can change quick. Better check regularly for updates on the HSA website!
And what Happens if I am Importing or Selling Health Supplements that are not Compliant with the Official Requirements?
This is not good at all. Your products will be seized. All people involved may get fined and/or go to jail. That means the importers, manufacturers, distributors and sellers of the illegal health supplements.
Check out this link for more information on that: http://bit.ly/SG-illegal-products-HSA
Better check with HSA if you have any further question.