Firstly don’t forget that Pakistan didn’t exist until British India was partitioned in 1947.
There’s no positively identifiable regimental or rank insignia in the picture, but the Sam Brown belt suggests an officer; having said that a specialist badge on his lower sleeve isn’t the norm for an army officer.
Did he have any other given names and do you have his year and place of birth?
There are a few G Matthews deaths at sea but only one G Mathews who died in India around that time you mentioned who’s listed in the GRO Index to Army Returns of Deaths.
Name: Matthews, George
Station : Fyzabad; Year: 1912; Page: 168
Age at death: 22
Using the above reference you can order a copy of the return entry from the GRO Southport, by post, telephone or online see http://www.gro.gov.uk/gro/content/certificates/default.asp
and click on contact us (RH list) for address and phone details.