From RIC your best bet for *A is probably either IAD or JFK.

It appears from the *A website that it is not possible to use US miles to upgrade on partner airline flights.

To get to SEAsia from IAD you would end up going via Tokyo most likely either on UA or NH. Or if you want to go the other way around there's the option of getting yourself to FRA or MUC on either UA or LH. From there you can go SQ or LH to SIN. Or if you want to fly US metal as much as possible to upgrade you can get to Europe via PHL or CLT and go from there.