I need to travel from NRT to Saigon SGN, but am finding a huge difference in the fares for a O/W than a R/T. I want to buy the R/T and just use the O/W.

The issue that I may see is that two weeks later I have a flight from BKK back to the US using JAL to NRT connecting on AA.

If I don't use the return leg for NRT-SGN will that affect my return trip on JAL from BKK to NRT?

Thanks in advance for any advice