The Association of Southeast Asian Nations (ASEAN , ) is a regional intergovernmental organisation comprising ten Southeast Asian states which promotes Pan-Asianism and intergovernmental cooperation and facilitates economic, political, military, educational and cultural integration amongst its members and Asian states.
 Since its formation on 8 August 1967 by Indonesia, Malaysia, the Philippines, Singapore, and Thailand, the organisation's membership has expanded to include Brunei, Cambodia, Laos, Myanmar, and Vietnam.
 Its principal aims include accelerating economic growth, social progress, and sociocultural evolution among its members, alongside the protection of regional stability and the provision of a mechanism for member countries to resolve differences peacefully.
 ASEAN is an official United Nations Observer.
 Communication by members across nations takes place in English.
In 2009, the Association of Southeast Asian Nations (ASEAN) established the ASEAN Intergovernmental Commission on Human Rights to promote human rights in the ten ASEAN countries.
 By mid-2012, the Commission had drafted the ASEAN Human Rights Declaration.
 The Declaration was adopted unanimously by ASEAN members at its November 2012 meeting in Phnom Penh.
 The Declaration details ASEAN nations' commitment to human rights for its 600 million people.
The US-ASEAN Business Council (also known as "the Council" or "USABC") is a leading advocacy group that aims to foster economic growth and trade ties between the United States and Association of Southeast Asian Nations (ASEAN)'s ten member countries.
 It is the only US-based organisation enshrined in the ASEAN charter.
 Based in Washington, DC, the Council has branch offices in New York City, Indonesia, Malaysia, Philippines, Singapore, Thailand and Vietnam.
 The 30-year-old Council represents over 140 of the largest US corporations, including AT&T, Chevron Corporation, Coca-Cola, ExxonMobil, General Electric, Intel, Philip Morris International, FedEx and Google.
The ASEAN University Network (AUN) is an Asian university association.
 It was founded in November 1995 by ASEAN member countries including 13 universities.
 After the enlargement of ASEAN by the ASEAN Charter in 1997 and 1999, the AUN membership has been increasing.
The 2017 ASEAN Para Games (Malay: "Sukan Para ASEAN 2017" ), officially known as the 9th ASEAN Para Games (Malay: "Sukan Para ASEAN ke-9" ), was a Southeast Asian disabled multi-sport event held in Kuala Lumpur, Malaysia, 17 days after the 2017 Southeast Asian Games from 17 to 23 September 2017.
 This was the third time Malaysia host the ASEAN Para Games and its first time since 2009.
 Previously, Malaysia also hosted the inaugural games in 2001.
The 2003 ASEAN Para Games, officially known as the 2nd ASEAN Para Games, was a Southeast Asian disabled multi-sport event held eight days after the 2003 Southeast Asian Games in Hanoi, Vietnam from 21 to 27 December 2003.
 This was the first time Vietnam hosted the ASEAN Para Games and the first time Timor-Leste participated at the ASEAN Para Games.
The Hanoi Plan of Action came about on the December 5, 1997, during the Second Informal Summit of the Association of Southeast Asian Nations (ASEAN), made up of Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam.
 During this Summit, ASEAN adopted the ASEAN Vision 2020, described as “a concert of Southeast Asian Nations, outward looking, living in peace, stability and prosperity, bonded together in partnership in dynamic development and in a community of caring societies."
 The HPA of 1997 was the first step in a series of actions to help ASEAN reach these goals.
The ASEAN Eminent Persons Group (EPG) was a group of prominent citizens from the Association of Southeast Asian Nations (ASEAN) member countries, tasked to create the ASEAN Charter.
 The group was formed on 12 December 2005 via the 11th ASEAN Summit Declaration in Kuala Lumpur, Malaysia.
Southeast Asian studies (SEAS) refers to research and education on the language, culture, and history of the different states and ethnic groups of Southeast Asia.
 Some institutions refer to this discipline as ASEAN Studies since most of the countries that they study belong to the Association of Southeast Asian Nations or ASEAN.
 Definitions of what constitutes Southeast Asia differ between scholars, which blurs the boundaries between Southeast Asian studies and other regional studies like Oriental studies and post-colonial studies.
 Southeast Asian studies incorporates anthropology, religious studies, linguistics, and international relations.
The ASEAN Charter is a constituent instrument of the Association of Southeast Asian Nations (ASEAN).
 It was adopted at the 13th ASEAN Summit in November 2007.

Question: The ASEAN Charter is a constituent instrument of a regional intergovernmental organisation comprising how many Southeast Asian states?  
Answer: ten