Anwar said the appointment was proposed by Malaysia and agreed upon by Thailand.
He expressed confidence that Thaksin's experience as a statesman would provide valuable insight for Malaysia's leadership of ASEAN next year.
"I have agreed to appoint (Thaksin) as my informal adviser on chairing ASEAN, along with a team of members from ASEAN countries in an informal setup.
"Thank you for agreeing to this as we need the benefit of the experience of such statesmen," he said during a joint press conference with his Thai counterpart, Paetongtarn Shinawatra, here today.
Thaksin served as the Thai Prime Minister from 2001 to 2006.
Malaysia will officially assume the chairmanship of ASEAN on Jan 1 next year, with the theme Inclusivity and Sustainability, which reflects Malaysia's aspirations for fostering a unified and prosperous ASEAN.
-- BERNAMA