Originally Posted by findark

I think you're better off sitting with the ticket as is.

Adding a fare break in LAX will almost certainly force LAX-BKK to full Y (due to standard int'l combinability rules). Trying to reissue the whole ticket in V could get the change fee waived, but you're going to have to worry about losing the confirmed TPAC upgrade too. Finally, W versus V is not going to make a huge difference in your chances of clearing EWR-LAX.

Also, if your connect in LAX is 24h00 or less, for future reference you should be able to get a single GPU to apply to all of EWR-LAX-NRT (assuming the latter is UA metal).