Maldives is UTC+5 and 2 hours behind Kuala Lumpur, so 8:15 am KL time would fit the timeline, plane must have been near fuel limit though.
Flight time from say Ho Chi Min City (Saigon) is a little under 5 hours at jet cruise. But presuming they were flying low, the total flight time would be higher.
Go with 5 hours +/-.
Do the time zone changes and flight times make sense?