Charles Gesner van der Voort (1916-1991) worked at Holland-China Trading Company (HCHC). HCHC had offices in Hong Kong, Shanghai, Tientsin (Tianjin), Rotterdam and London. Director at the head office in Rotterdam was Willem Kien, who worked in Hong Kong and Shanghai for the firm. He made this photo.
These men look like they are taking a break to enjoy their food. The person with the large round hat could be a woman. Looking at the clothing and vegetation, it is probably spring or summer.
Courtesy Kien family archives