Ng taught a variety of courses focused on environmental impact assessment (EIAs), nature conservation, sustainable development, and water governance.

[19][20][21] In 1999, Kowloon-Canton Railway Corporation proposed to construct a Lok Ma Chau spur line which would cut through the wetland of Long Valley, Hong Kong According to the Hong Kong Bird Watching Society, the construction of the spur line threatened to destroy habitat of over 210 avian species and 13 globally-threatened species.

[23] As the director of the Conservancy Association, Ng lobbied for international support for the "Save Long Valley" campaign and wrote many letters to various Hong Kong government officials urging them to scrap the proposed spur line, stating that the KCRC claims in its environmental assessment report were "flawed" and "contradictory.

"[23][24] He conducted his own environmental field work and argued that there could be alternative ways to construct the spur line "without destroying the natural habitat and biodiversity at Long Valley.

[27] On October 16, 2000, the Hong Kong Environmental Protection Department (EPD) rejected the KCRC's Lok Ma Chau rail project.

[36] In an interview for China Daily in 2017, Ng described the focus and goal of the JC-Wise project was to encourage the Hong Kong public to adopt a "river-friendly" culture mindset: "Every river has its own story.

[43][44][45] Ng also worked with Lam Chiu Ying on the ongoing sustainable rural revitalization of Lai Chi Wo, a 400-year old Hakka village in Hong Kong.

[48] The program is the "first cross-sector partnership of its kind implementing sustainability initiatives and innovation in farming, training, education and research" in Hong Kong.

[50][51][7] The plan to revitalize Lai Chi Wo was initially met with some objections by local Hakka villagers "fearing commercialization and damage to nature and heritage.

The project was recognized for upholding "the key dimensions of sustainable development – economic, social and environmental – in undertaking the holistic rejuvenation of the historic Hakka agricultural settlement using nature-based solutions ...

Drawing upon indigenous know-how, geomancy principles, and conservation science, the project demonstrates the importance of interweaving nature and cultural heritage in setting a new urban-rural sustainability agenda for Hong Kong SAR and beyond.

[62] His decision to advise Leung was viewed by some as politically controversial, but Ng "believed the new leader could make a difference in environmental policy.

"[62] Ng was awarded the Silver Bauhinia Star by Leung in 2014 for his "distinguished public and community service" and "exemplary efforts in serving on the Transport Advisory Committee and the County and Marine Parks Board.

[67][68] Ng later served as the Director of the Mai Po Nature Reserve and the Flyway Programme of WWF Hong Kong.

[62] On June 3, 2000, he read his personal essay titled "Letter to Hong Kong" on the RTHK radio program「香港家書」, stating that his "work and struggle" for the environment, specifically Long Valley, gave him "encouragement to fight against cancer.

[62][75] Senior Hong Kong government officials issued the press release statement on the news of his death, stating "[We] are forever grateful for his valuable advice to the Government on issues relating to city planning and development, greening, nature and heritage conservation, and on promoting sustainable development in Hong Kong.