The full form for the ASEAN is:

Association of South East Asian Nations

The correct answer is option (1) - Association of South East Asian Nations

ASEAN stands for the "Association of Southeast Asian Nations."
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.
With some of the fastest-growing economies in the world, ASEAN broadened its objectives beyond the economic and social spheres. In 2003, ASEAN moved along the path of the EU by agreeing to establish an ASEAN Community comprising three pillars, namely, the ASEAN Security Community, the ASEAN Economic Community and the ASEAN Socio-Cultural Community.