I wouldn't be to alarmed if I were you. Perhaps KE is in the process of deciding its discount fares and all you are seeing now are full fare tickets. This is common with the Japanese airlines as well, which often do not publish discount fares for certain routes until about three months before the travel dates.

I think that $1,300 sounds like a great fare to BKK from WAS or NYC, so if I were you I would consider buying the ticket on UA or NH if the flight times are good for you.

It is too bad that you missed the $900 fare on KE which seems unbelievably low, but I would not count on that fare coming back. It might be a good idea to just get the $1,300 ticket before that goes up.