McCain died of brain cancer Saturday in his home state of Arizona.
Opposition Cambodia National Rescue Party was dissolved by court last year for alleged complicity in treason plot.
No reason specified for pardons, but they come just days after a sweeping election victory by Hun Sen's ruling Cambodian People's Party was officially certified.
The three men were all facing deportation to Cambodia despite having served their sentences and living in the US as lawful permanent residents.
Wirapol Sukphol sentenced to more than 100 years in connection with funds he fraudulently raised from followers.
The annual meeting of the 10-nation bloc opens with security concerns.
Dam collapsed Monday, releasing large amounts of water that swept away houses, flooded villages, and made more than 6,600 people homeless.
The victory could extend his boxing career, which had taken a backseat to his political life.
Foreign helpers, including some of the world’s best cave divers, also began travelling home.
In January, Taiwan prosecutors said they found evidence that China's Taiwan Affairs Office promised to pay a Taiwanese politician $500,000 to run a website publishing articles promoting unification.
The Hollywood-movie storyline embraced the best of technology and was void of divisive politics.
More than 50 people were unaccounted for as of Tuesday morning.
The boat was one of two that overturned in bad weather off the resort island of Phuket.
Radio Free Asia spokesman Rohit Mahajan says RFA told authorities that it was unwilling to bow to their pressure to use a term other than Rohingya to describe Muslim minority.
Speculation over how N. Korea will handle summit costs has taken off after Washington Post report cited anonymous US officials suggesting Trump administration has been 'seeking a discreet way' to help pay Kim's hotel bill.
The ruling National Front might lose the popular vote but still win a majority in Parliament thanks to an electoral system that gives more power to the party’s traditional supporters.
Bersih, a group promoting free and fair elections, says it has found "major irregularities'' in the electoral roll, including more than 2.1 million people without addresses.