Thanks to Patricia for sharing the ID of this hoverfly on 2 August 2020 and pointing out that there are another similar-looking hoverfly (Asarkina porcina) in Singapore. I could not tell the difference between the two but since there were slightly more (5 versus 3) sighting of Asarkina salviae in Singapore posted on iNaturalist website (viewed on 2 August 2020), I will keep to this name.