Via The Flight Deal, you can fly round-trip in coach from New York, Chicago, San Francisco, and Los Angeles, to Jakarta, Bangkok, or Ho Chi Minh City for ~$365+. You can even fly into one city and leave from another with this deal, so you can see 2 Southeast Asian cities for cheap!
I found a flight from New York (LaGuardia) to Ho Chi Minh City on September 20, 2016, and returning from Bangkok on September 27, 2016, for ~$429.
And a ticket from San Francisco to Jakarta on October 5, 2016, returning from Bangkok on October 12, 2016, for ~$395.
These fares are valid for travel on ANA from September 2016 through early December 2016.
Here are the details. And how to search for these deals!