Sangju, North Gyeongsang Province (South Korea)

The flag of Sangju is white with mark.
http://www.agrinet.co.kr/news/articleView.html?idxno=162740
Tomislav Šipek, 27 August 2019

From the Sangju website:

City Flag

Symbolizes the Three Whites originating from the shapes and colors of rice, dried persimmon and cocoon which are the special products of Sangju.

Embodies the letter "S", the initial of "SANGJU" and the Nakdong River that calmly runs, and represents the road of development and progress toward the future.

As the seed of rice is shooting out its bud, it implies a progress toward the new world.

The general shape of the Taegeuk stands for harmony and unity of citizens and also represents that Sangju is the center of Korea

researched by Phil Nelson, 13 October 2005