Maj Thomas was the manager of Foy & Gibsons, a department store (like Myer) that was located on the corner of Swanston St and Bourke St, now the Bourke St mall. His mess dress has ordnance badges. l doubt that he was in anything to do with engineers as he would struggle to use a screw driver ! His full name is Arthur John Thomas and known as John. I know that he was on the reserve officers list for many years.
Regards
Phil.
The Ordnance Corps , RAAOC, would have had an engineering branch which later became RAEME and an officer would not necessarily need engineering skills.