What should normally happen when displaying a mapshape is that it should be shaded in fully, without any extra shading or boundaries double shaded. However, for Thailand and Singapore, this does not happen, instead the Kartographer giving a weird double shade over the core of the country. Examples at https://en.wikivoyage.org/wiki/User:SHB2000/TH and https://en.wikivoyage.org/wiki/User:SHB2000/SG.
What should happen is something that looks like this (https://en.wikivoyage.org/wiki/User:SHB2000/SK).
Other information (browser name/version, screenshots, etc.):
As far as I can see, https://www.openstreetmap.org/relation/536780 and https://www.openstreetmap.org/relation/2067731 appear to look completely normal. At least from a cursory look, this seems to be more of an issue on our end than on OSM's end.