Bai is specialised in the development and evaluation of complex health interventions in both LMICs and HICs. She leads co-creation between academics and policy makers to tackle leading global health challenges such as obesity, and has co-authored with policy makers from 31 countries. She has led multi-nation, inter-discipline research projects to generate impactful scientific outputs used by international bodies such as WHO, United Nations, World Obesity Federation, European Commission, Asian Development Bank, the State Council of China and Switzerland Federal Food Safety Office. She has a track record of leading international advocacy and methodological innovations of methods rooted in system science. She leads the SYSTAM International Consortium, comprising Ministries of Health in the SEA region and WHO offices to develop and monitor systemic, national level interventions tackling all forms of malnutrition. She led methodological innovations to systems methods for tackling multiple global challenges simultaneously. These innovations are endorsed by the WHO headquarters for international applications. She led the development and publication of the first reporting guidance for public health intervention projects underpinned by a systems approach. She designed and co-edited the first journal collection dedicated to systems approach to tackling global nutrition challenges (72 authors from 13 countries, >10 million article views and downloads internationally). She has organised and chaired many international symposia in different countries to share the first empirical experience of applying a systems approach to nutrition interventions in HICs and LMICs. She led the evaluation of the world's first, multi-setting regulatory intervention on sedentary behaviour among children, providing the first, real-world evidence for regulatory interventions on sedentary behaviour. 

Bai leads the City Futures Theme at the Cabot Institute for the Environment.