This gets very complicated.

In checking correct examples of Eilema prabana one thing did not match well.
There should be a dark patch on the prothorax.

E. prabana.

http://v3.boldsystems.org/index.php/...e?taxid=588636
http://v3.boldsystems.org/pics/LEPMY...1399648792.JPG

https://www.researchgate.net/figure/...fig1_267642363

http://virtualcollections.naturalsci...sa-tams-1935-1


Singapore do have Brunia antica & E. prabana.

E. prabana is described as very dark ie blackish grey.
http://www.mothsofborneo.com/part-7/...siini_10_1.php


Brunia antica in Singapore.
https://www.inaturalist.org/observations/777156
https://www.inaturalist.org/observations/14695527

Likely Eilema prabana. Prothorax with a dark patch.
https://www.inaturalist.org/observations/8488541
https://www.inaturalist.org/observations/8427538

The width of the yellow margin is likely a variable feature.


Thus it is much more likely your pix are Brunia antica , that is if B. sarawaca does not occur in Sumatra.


TL Seow : Cheers.