Help with uniform please

[alor]

Please could someone help identify the uniform in this photo of Frank Henry Card (1895-1958). We'd always thought he served in the Army during WW1 but I've never found a medal card that fits him. Recently I've found an entry for a F H Card as a Rigger in the Air Force and wonder if this was him. As he's wearing shorts could it be some sort of tropical military uniform?
If it is a RNAS/RFC/Air Force uniform do any service records survive? I do know after the war he served in the Merchant Navy
I'd be grateful for any help
Alor   

[scrimnet]

If you can do a close up in high res of the shoulder title, it may help pin him down. Prior to 01 Apr 1918 and the formation of the RAF, men served in the services you mentioned, but when the medal cards came to be written, they were all RAF so they were listed thus.

This is an Army uniform, witnessed by the army good conduct chevron, and he is in the middle or far east when this was taken.

[alor]

Many thanks – unfortunately I don’t have access to the original photo so can’t supply a higher res version
The medal card we originally found was for a Pte Frank Card, RASC, Regimental no: S4/061181. It does also say he served in Egypt so could fit with the tropical uniform.
However in the absence of a service or pension record I’ve always been suspicious this was actually him as in all other official documents he was Frank Henry Card or F H Card.
Does his regimental number S4/061181 have any significance?

[mmm45]

you can make out  ASC shoulder title
S4 means he worked in Supplies and was part of 4th New Army

Ady