Vertical oval integlio chop
the center seem to be a two-eagle used in the Lesser Austrian Imperial Arms (Kleines österreichisches Reichswappen) 1867-1915
http://www.crwflags.com/fotw/flags/ah).html


Austro-Hungarian Consulate in Bangkok used a similar but circular handstamp that stated:

K. KOESTERR UNGAR CONSULAT IN BANGKOK

at the bottom of the oval is SINGAPORE
on the left side
at the top -... NCAR  ...
on the right ... AT...