Which of the following nations joined the ASEAN after the formation of the association?

Vietnam

The correct answer is option (2) - Vietnam

ASEAN was established in 1967 by five countries of this region — Indonesia, Malaysia, the Philippines, Singapore and Thailand — by signing the Bangkok Declaration. The objectives of ASEAN were primarily to accelerate economic growth and through that ‘social progress and cultural development’. A secondary objective was to promote regional peace and stability based on the rule of law and the principles of the United Nations Charter. Over the years, Brunei Darussalam, Vietnam, Lao PDR, Myanmar (Burma) and Cambodia joined ASEAN taking its strength to ten.