Grandson of Ng Chun So originally his student until he passed away. He then became Yip Man's student until 1968 when he moved to Korea. Master So was by profession an Acupuncturist, herbalist and Chinese Restaurant owner and manager who had his kwoon upstairs from his clinic and restaurant and taught two versions of Wing Chun as Ng Chun So's and Yip Man's styles were slightly different. Ng Chun So was not Ip Man's student. In fact he was Yip Man's elder Wing Chun Brother and possibly directly a blood descendant of Yim Wing Chun. Sifu So taught both methods as well as both Yang and Wu styles of Tai Chi.
Due to the large number of American soldiers and a more open mind towards foreigners by the Chinese community in Seoul, Sifu So may very well have been the first Sifu other than Bruce Lee to teach Americans and other foreigners. However he never had more than a handful of students as Wing Chun was not his bread and butter. According to his granddaughter San So Yuen, Sifu So passed away on June 11, 1995.
Source San So Yuen, granddaughter of Sifu So Duk Sun.