The global warming caused by the ever-increasing emission of greenhouse gasses has been challenging all countries to do a response embracing the needs and interests in Vietnam, known as one of the poor countries, would be the most seriously affected by climate change, especially by sea level. Meanwhile, Japan is moving forward aggressively to become a major global player in Smart Cities with one of the main purposes of exporting low-carbon technology to developing countries in South-East Asia through some green projects after the Japan’s earthquake. That is the reason we focus on the promising ‘Smart City’ project for considering the suitable investment in long-term development in energy security and climate change in Vietnam. However, it requires huge investment financial amounts and long-term to profitability under uncertainty. Hence, PPP (Public-Private Partnership) is an attractive scheme to optimize the trade-off between Vietnamese government-owned corporation (seeking for technology and capital) and foreign private firms (for market demand and carbon credits through CDM). In a context of a strategic partnership as a competition method, the option-games as a methodology analyze the relationship of competition and partnership between foreign firms and the Government owned-corporation for irreversible investment under uncertainty and competitiveness. Then the result from Crystal Ball and OptQuest stimulation (one of stochastic optimization tools in simulation software Crystal Ball) is significantly useful to analyze the optimized value of Project.