Nam-Hai Chua has made many original contributions to plant cell and developmental biology. He discovered the D2 protein and other chlorophyll–protein complexes related to the photosystem II reaction centre. With others, he demonstrated that the small subunit of RuBisCo is synthesised as a precursor on free cytoplasmic ribosomes and uncovered many of the details of its subsequent transport into the chloroplast. His laboratory demonstrated that the cauliflower mosaic virus 35S promoter can be used to transcribe heterologous coding sequences in transgenic plants. This strong, constitutive promoter has become an important tool in basic plant biology research and is also widely used to express transgenic traits in crops. 

His current work on the control of gene expression in transgenic plants is laying the groundwork for new advances in plant breeding. Nam-Hai serves as scientific adviser to companies and government-related organizations in several countries.