The post-cold war refers to the collapse of the Soviet Union in 1991 to the present. To discuss the security challenges facing Southeast Asia in the post-war era, there is necessary to mention about how the security challenges change from the cold war era to post-cold era. During the Second World War, the security order within the Southeast Asia was mainly influenced by the two superpowers, which were the USA and the USSR. As the WWII ended, the Cold War begins, the Southeast Asia region was quickly carved out by the former colonial powers as their sphere of influence. Since the USA had played an important role that liberates the Southeast Asia during the WWII, the USA started to act as a dominant role that claimed to safeguard the independence of the countries and prevent the communist from invading the region. In other words, the USA wanted to stop the USSR and China from entering the Southeast Asia. Although the USA was defeated in Vietnam War, it continue to maintain an off-shore presence in Southeast Asia region. On the other hand, from 1967, Thailand, Malaysia, Philippines, Indonesia and Singapore established Association of Southeast Asian Nations (ASEAN). Until today, over five decades, ASEAN has been a significant regional organization that pursuing particularly the region security and peace in order to develop their economic. As Adam Malik stated, “ASEAN can be seen as reflecting the growing political will of the nations of this region to take charge of their own future, to work out problems of their development, stability and security together and to prevent their region from continuing to remain the arena and the subject of major power rivalry and then conflict (qtd in. Shee, 754).” However, at that time, the fundamental of the ASEAN system was still very weak and turbulent and if ASEAN wanted to construct their region security they had to rely on the external forces. Therefore, there still have been many fragmentary conflicts. And it was not until the collapse of the USSR that stopped the turbulent condition and created a new Post-Cold War security environment in the Southeast Asia. After the Cold War, the colonial powers leaved, the Southeast Asia region has been in a stable and peaceful condition. According to Hassan, “Among the constructive and stability-inducing forces at work in the region is the absence of serious inter-state conflict, bilateral arrangements for enhancing cooperation and dispute management, and the culture of cooperation based on mutual interest that is being fostered by the Association of Southeast Asian Nations (2006).” It is true that the regional cooperation offers several benefits, for example, increase economic bargaining power and minimize feelings of insecurity (Shee). In addition to those positive outcomes after the cold war, there do have some security challenges happening within the Southeast Asia. According to JÜRGEN RÜLAND: “interstate wars and other conventional security threats, such as territorial disputes and arms races, have subsided, while the region is increasingly confronted with non-conventional security risks emanating from international terrorism and organized crime, separatism and piracy, irregular migration, poverty, environmental issues, energy shortages, economic crises, pandemics such as HIV/AIDS and SARS, and natural disasters such as the devastating tsunami that hit the coastal areas of Sumatra, Malaysia, Thailand and Burma/Myanmar on 26 December 2004.” In short term, that non-conventional security threats have emerged and replaced inter-state confrontation in Southeast Asia region. To address the security challenges confronting Southeast Asia, I think the human security is one of the important issues. Nowadays, the political system in some of Southeast Asia countries still remain unsteady. Although the democratization has been widespread during the post-cold war era and even today, there are still several semi-democratic, nominally socialist and overtly authoritarian regimes in the region. For example, Thailand’s frequent coup detat. As a result, the failed political system lead to the human security issues. According to UNDP’s benchmark, half of the regional states have low human development. Between one-fifth and one-third of the population in Cambodia, Laos, Myanmar, Philippines and Vietnam subsist below the national poverty line. Indonesia, with 18 percent or 40 million people estimated to be living below the national poverty line, is not far behind. As a result of the poverty, the people can not enjoy the basic health life and often suffer from hunger. On the other hand, the human rights violation. In Thailand, researchers, environmental activists, academics, journalists and others also face arrests, criminal investigations, and prosecution (Patel, 2017). Also, in Myanmar, after Aung San Suu Kyi’s National League for Democracy hold the power, they modified several unfair and repressive rule created by the military government, however, the new government does not give the minorities the same rights. The Rohingya community in northern Rakhine state has been discriminated by the Myanmar government and it was reported by the UN that the Myanmar government was conducting an “ethnic cleansing (“Rohingya “, 2017).” The second security challenges that concerned the Southeast Asia is maritime security issue. Due to the maritime geography advantage of the Southeast Asia region, the region is blessed to have the abundant resources and the ocean also play an important role in their economic progress and national income. According to the Maritime Security Desktop Exercise (MSDE), the Southeast Asian States which participated in 2, 3 and 4 held in 2011, 2012 and 2013, were recognized that piracy, maritime terrorism, people smuggling and IUU fishing were deemed to be the primary maritime security threats in Southeast Asia (2011-2013). In addition to those pure maritime problems, there is also a maritime area issue in the Spratly archipelago of the South China Sea and there are at least six countries, China, Taiwan, the Philippines, Malaysia Vietnam and Brunei have claimed the sovereignty of the island. The last security challenge I would like to address on is the terrorism. The terrorism security challenge has not be the issue that only being considered in the Southeast Asia, however, it is a global issues that concerned all of the countries. After 9/11, the main challenge of the terrorism is its increasingly transnational organization and the fact that it is often directed against ‘soft’ targets and civilians, inflicts unacceptable harm, and threatens the credibility of governments to protect their populations (Tellis, 2004: 41). For example, the international terrorist groups, as al Qaeda and Jemaah Islamiyah (JI), and there were some terrorism happened in the region, such as in Bali (October 2002), Jakarta (August 2003 and September 2004) and the Philippines (February 2003 and February 2004). Moreover, there are 200 millions Muslims live in the Southeast Asia region. With the Islamic terrorism increasing recently, such as ISIS and al Qaeda, there is a certain concern that the Southeast Asia might become one of the basement of Islamic terrorism. Although it has been said that the Islam in Southeast Asia region has a tolerant, moderate, peaceful that is different from the Islam in Middle East which prefers more doctrinaire varieties and it is undoubtedly that . However, it soon became clear that the region was vulnerable to the invasion of violent Muslim militants as the discovery of networks affiliated with al Qaeda in Malaysia, Indonesia and Singapore (Ott,2006). It is obvious that the Southeast Asia has progressed a lot after the end of the Cold War, for example, the establishment of the ASEAN, which enhances the bilateral military cooperation in this region, as well as, its rapid economic development has later brought the stability to the ASEAN countries. Without the colonial power, the countries start to establish their own economic, political and the future. However, maybe it was because of the fragile democratization and political system, there still have some new security challenges emerged in the Southeast Asia in the post-col war era. As I mentioned above, for example, the human security challenges of Rohingya happened in Myanmar; the maritime security challenges, piracy, maritime terrorism, people trafficking and the violation of IUU fishing, moreover the maritime area issue in the Spratly archipelago of the South China Sea; last, the terrorism security issue, the local terrorist group Jemaah Islamiyah (JI) and transnational terrorism. Unlike the cold-war era, without the presence of those great powers who used to occupy the region, there are concerns if the Southeast Asia cannot deal with the problems properly that the challenges could lead to the collapse of some countries in the region. However, according to Professor Sheldon Simon, who has written on Asian security for over 40 years, argues that ASEAN is pursuing an engagement strategy in the 21st century, bringing the great powers (the United States, China, India, Japan, and the European Union) into Southeast Asia’s political and economic discussions (2014). Based on this information, it seems that ASEAN’s strategy is to invite the external powers to help them dealing with the problems. And in my opinion, with the growing status of the Association of Southeast Asia Nations, it is possible that the external powers will come back and contribute to the future improvement of the regional security challenges.