Don't think it's been asked but I was wondering if there are specific fare codes that would not be upgradable? Specifically now that TG doesn't give points to codes G, V & W. If you wish to seek a stand-by u/g can you do so from the cheapest available fare?

I guess that it would be a wise investment to pay the small fare difference anyway to collect the miles should the u/g not clear.

I'm planning to try the stand-by thing next month for BKK-DPS. Hopefully it works. Does anyone have any experience with this route and can make observations on how the loads are and u/g success?