There is 1 species endemic to Sumatra : M. baliochraspedus, but i can't find any documentation about this species so i can't compare with the one i found. The only description of this species is in Heterocera. Collected in Korinchi, West Sumatra, by Messrs. H.C. Robinson and C. Boden Kloss J. Fed. Malay States Mus. 8 (3) : 107-139
But i can't access this publication.
Holloway in MoB part 13 (not available on line) state that apart from those mentioned in the book (Bornean spp) there is a baliochraspedus from Sumatra & atropunctata from JAva which may be conspecific. P. Malaysia have two unnamed spp.
In other words in 2010(publication of article) there were only three known species in Sumatra namely, M. atrigutta, niasica & baliochraspedus.
The first is widespread & the 2nd in Sundaland.
Your images matched the description of M. niasica very well. The zone between the marginal spots & the postmedials have three pink patches & a small triangular one adjacent to the middle marginal spot.
M. baliochraspedus was described by Rothschild in Journal of the Federated Malay States in 1920.
It would be quite arduous to go to the National Museum, get the necessary permission to seek out this publication.
Most of the species are alike .Even with the book on Borneo species it is hard to ID as much is dependant on the genitalia.
For example in the link given below I think it is not M. collina but rather M. santubong.
Holloway said of M. collina the pink patches in the respective zones tend to merge, ie they would have form two main broad pink bands. https://www.projectnoah.org/spottings/13023135