Born as Ng Duk Sun on Jan 14, 1917, he was a grandson and student of Ng Chun So from 1925 until 1938 and then Yui Choi from 1938 until 1949.
He changed his name to So Duk Sun to escape communist China and moved to Hong Kong in 1949. He was a friend of Ip Man's and they practiced together often until 1968 when he moved to Korea. However Yip Man was not his teacher as they were both Grandmasters.
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. He also taught Pakua, Hsing-I and Tai Chi.
He passed away on 11 June 1995 in Singapore.
Source Ng Ai Lun, great Granddaughter.