More than 600 million people live in the ASEAN countries that will join the bloc when it launches in December. That's about 100 million more than the EU.
Leaders in six countries, including Thailand and Singapore, have already removed tariffs as part of the deal.
Those in Vietnam, Cambodia, Myanmar and Laos will follow suit by year's end with some exceptions.
They say they'll improve visa access for doctors, accountants, and other types of skilled workers.
Leaders in all countries will ease equity restrictions to make it easier for foreign companies to do business.