Buan County, North Jeolla Province (South Korea)

Here is correct flag, white with mark.
http://news1.kr/articles/?3372287
image by Tomislav Šipek, 19 November 2019

From http://www.buan.go.kr/english/politic/pol_04.jsp:

Background (white) symbolizes the purity and warmth of the Buan people

Arc (red) symbolizes the town of beautiful sunsets with the tradition symbolize the center for tourism with harmony, dream and future.

blue symbolizes the crystal clear sea water of Buan

Green symbolizes the eco-friendly environment, rich mountains and plains

navy blue symbolizes the dynamic expresion towards the future full of hopes

researched by Phil Nelson, 29 March 2005