It's about 22-23 hours in the air from Miami to Phuket. About two to three hours more than for me. But you will have to change flights at least twice and perhaps three times depending which airline you chose. The layover lengths at those two or three stops will really determine the length of the trip.I read something like 30 hours from US to phuket
Kayak.com shows the total time of the trip. Also the time of each leg and layover if you click on details.










