In order to promote ASEAN gas market integration, this paper offers four scenarios to renew momentum towards continuing with the marginalised Trans-ASEAN gas pipeline (TAGP) and further development of cross-border pipeline gas trading. The four subregional and regional market integration scenarios could be used as stepping-stones to achieve ASEAN gas market integration. The impact of each scenario was estimated with the least cost world gas market model and the impact is indicated by the difference between each integration scenario and the baseline scenario, respectively. The simulations suggest that integrated gas markets in ASEAN are beneficial through the reduction of total procurement costs for ASEAN and the World. The TAGP is also beneficial in terms of incentivising ASEAN production that can be transported cost-effectively to demand centres within the region. The development of marginal production due to the availability of lower cost transportation is in line with ASEAN's goals for resource optimisation and energy security enhancement. The paper suggests that ASEAN should advocate the gas market integration, and that ASEAN member states could take various institutional measures to achieve higher levels of integration.