His scheduled appearance in the northern Thai city of Chiang Mai from Sunday comes as Iran gears up for elections and as world powers press the Islamic republic over its suspected nuclear program and support for the Syrian regime.
Ahmadinejad, who is constitutionally barred from seeking a third straight term in next month's polls, is set to join regional leaders at the Asia-Pacific Water Summit, which will focus on water security and climate change.
Ahmadinejad -- who has irked the West since taking office in 2005 with his defiance of nuclear inspectors, fierce criticism of the US and Israel and tough response to opposition protests -- is set to address the summit on Monday.
The race for Iran's highest elected office has intensified since former president Akbar Hashemi Rafsanjani and top nuclear negotiator Saeed Jalili officially registered for the June 14 election.
Ahmadinejad has endorsed his controversial aide and ex-chief of staff Esfandiar Rahim Mashaei.
Iran has also come under pressure over the conflict tearing apart its close-ally Syria and has repeatedly rejected calls for foreign intervention in the increasingly brutal war.
