The Association of Southeast Asian Nations took a major step towards becoming an EU-style community on Monday with the passing into force of a new charter setting benchmarks for democracy.
The charter sets out rules of membership, transforms ASEAN into a legal entity and envisages a single free trade area by 2015 for the region of 500 million people.
It came into force with a meeting of ASEAN foreign ministers at the bloc's Jakarta secretariat, 30 days after Thailand became the last member to deposit its ratifying documents.
"This is a momentous development when ASEAN is consolidating, integrating and transforming itself into a community," Indonesian President Susilo Bambang Yudhoyono said.
"It is achieved while ASEAN seeks a more vigorous role in Asian and global affairs at a time when the international system is experiencing a seismic shift," he added, referring to climate change and economic upheaval.
"Southeast Asia is no longer the bitterly divided, war-torn region it was in the 1960s and 1970s."
ASEAN consists of Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam.
The charter was supposed to have been activated at a summit in Thailand but that meeting was postponed by a domestic political crisis, which has underscored the fragility of democracy and human rights across the region.
Thai Information Minister Mun Patanotai presided over the presentation ceremony as representative of the bloc's current chair, as the country lacks a foreign minister to do the job.
"From a loose association of countries in the past, ASEAN is now a legal entity that aspires to become an ASEAN community in the future," he said.
"With greater peace and stability the region could focus on trade, production and investment," he added, at the end of a year in which his own country has been engaged in an armed standoff with neighbour Cambodia over a border dispute.
The ceremony was overshadowed by the crisis in Thailand, where lawmakers on Monday elected opposition leader Abhisit Vejjajiva as the country's third prime minister in four months after half a year of crippling protests.
The turmoil left 350,000 passengers stranded at Bangkok's international airport earlier this month and has badly hit Thailand's image and its economy.
"In spite of the political setback in Thailand, which is now the ASEAN chair country, I believe ASEAN will not and cannot be slowed down," ASEAN Secretary-General Surin Pitsuwan said at the ceremony.
"Regional co-operation and economic integration to build the ASEAN community will actually shift into higher gear after the entry into force of the ASEAN charter today."
The charter will give the bloc, much maligned as a talking shop, greater clout in international negotiations but critics argue that some member states will continue to get away with gross human rights abuses.
The bloc's proposed new rights body has no teeth and the charter has no provision to sanction members like Myanmar, where the junta has kept democracy leader Aung San Suu Kyi under house arrest for most of the past 18 years.
The country's secretive junta is under European Union and United States sanctions over its human rights record.
No date has been set for the creation of the planned rights body but a first draft of its terms of reference will be handed over to a meeting of foreign ministers in Thailand in July, officials said.