The Association of Southeast Asian Nations (ASEAN) meeting in Phnom Penh will focus on security and territorial disputes in the South China Sea.
Also on the agenda, however, is a move by host Cambodia to ease tensions on the Korean peninsula.
At a time when North Korea is in the grip of international sanctions, Cambodia has embraced the secretive nation.
Aiming to play peacemaker, Cambodian officials went to Pyongyang last month in the hopes of moving beyond February's missile test, which was conducted by North Korea in defiance of UN sanctions.
They say North Korea is ready to talk, but wants respect. Cambodia hopes its closer relationship will give it a greater chance of success.
Al Jazeera's Steve Chao reports from Phnom Penh.