So, Chateau, I find that your conclusion about SilkAir being the airline Ty/Aja used to fly into Siem Reap to be correct. Since May 4 was a Ssunday(not a Monday as I reported earlier), then MI616 was available to Ty/Aja. Sicne that would have been their best option once in Singapore that morning, it is very likely that they took it.
SILKAIR WEEKLY FLIGHTS SINGAPORE TO SIEM REAP
Flight Depart Arrive Duration Stops Mon Tue Wed Thu Fri Sat Sun
MI 616 Singapore 10.20 am Siem Reap 11.35 am 2h 15m 0 x
MI 618 Singapore 4.10 pm Siem Reap 5.20 pm 2h 10m 0 x
MI 622 Singapore 8.40 am Siem Reap 9.50 am 2h 10m 0 x x
MI 630 Singapore 7.55 am Siem Reap 11.35 am 4h 40m 1 x
MI 633 Singapore 2.35 pm Siem Reap 3.50 pm 2h 15m 0 x x
MI 636 Singapore 1.55 pm Siem Reap 5.35 pm 4h 40m 1 x
EDITOR's NOTE - the revision above was the result of feedback from Slowhatch and results in totally different conlcusions.