Hi there!
You can check out
www.seoulmall.com.sg (they carry genuine Korean Red Ginseng products from Korea). And their prices are lower than retail stores. But be prepared to wait up to 7 days for the products to be sent from Korea to you.
Alternatively, if you cannot wait, you can buy from offline retailer. One of them is located at Takashimaya, but the prices are incredibly expensive.
I also love Korean Red Ginseng! Hope the above info helps!
Cheers!