Looking at the 1935 & 1940 Singapore & Malayan Directories:
a F.J. HOLMBERG worked in the Ore Buying Dept,Straits Trading Company, Ocean Building, Singapore.
A M.P. HOLMBERG worked for Boutcher & Co., Chartered Bank Chambers, Singapore.
An N. Holmberg was in 1940-1941 a Private in the Signals Section, HQ Company, Ist Battalion [Singapore] Straits Settlements Volunteer Corps.
There are also 6 Holmbergs in the 1900 Straits Directory - mostly in Malaya.

best wishes

Jonathan Moffatt

Malayan Volunteers Group