[7][8][3] His maternal cousin was the Dutch-Indonesian suffragist Thung Sin Nio (1902–1996), while his paternal great-nephew, Phoa Liong Gie (1904–1983), would later attain prominence as a jurist, politician and newspaper owner.

[3] To be with his wife, Phoa moved to Batavia, the capital of the Indies, where his father-in-law sat on the city's Kong Koan or Chinese Council.

[3] The couple's only child – a daughter named Phoa Tji Nio – went on to marry Khouw Kim An, the 5th and last Majoor der Chinezen of Batavia.

[14][3] Phoa proved very outspoken and, partly thanks to his own and his wife's family background, soon came to be viewed as a leader of Batavia's Chinese community.

[1] In 1900 Phoa, together with his former classmate Lie, was an establishing member of the Tiong Hoa Hwe Koan (THHK), a modernizing Confucian organization.

[15][16] THHK aimed to purify the practice of Confucianism in the Indies, and ran a network of around 130 schools to promote a modern education for the colony's ethnic Chinese community.

[15][16][4] He served as the President of THHK for twenty-three years before retiring,[1] and was assisted by the philanthropist (and his son-in-law's cousin) Oen Giok Khouw, as vice-president.

Together with the politician H. H. Kan and the bureaucrat Kapitein Nio Hoei Oen, Phoa was part of the committee that raised 500,000 gulden towards the establishment of the Technische Hoogeschool te Bandoeng (today Institut Teknologi Bandung), which was founded in 1920 and is now one of Indonesia's oldest universities).