A cautionary note, an hour after changing my SIN-DPS leg I went to select seats on the SQ website and it did not list this leg. AS website, which previously listed the leg, no longer listed it. I called AS, which had a 3 to 4 hour wait time, and selected the call back to be called back 4 hours 45 minutes later. AS had the DPS leg showing but 5 days after the date I booked (and which did not list on SQ or AS websites). Gave the agent the DPS flight details, agent did not listen and put me on the wrong flight for the day I wanted, got him to fix it, process took 15 minutes as the agent had to keep going back to the international desk.