Direct flights on SQ from SIN to HKT (Phuket). I would choose Trisara, but Amanpuri, Anantara Layan, and Rosewood could be options. With such little time, a direct hassle free flight on SQ, and then being whisked off to a nearby resort like Trisara reduces time spent in transit. You can be in your villa within a few hours of leaving Singapore, instead of waiting for a connecting flight in Vietnam.