Dear K.Chet,
If you would like to change to TG 414 for your return flight you must to pay the different fare and the fee for change THB 5,800.- (Price is not guarantee) because you have to upgrade ticket validly 1 month to ticket validly 6 months instead. For now TG414 is not available on the class of ticket 1 month. If you would like to change please confirm back soon as soon possible ka.