Teacher Denis Bates, 30, was taken to Phuket International Hospital then to Vachira Phuket Hospital after his 132.5cc Yamamha Nouvo motorcycle left the road at speed on a curve.
He was travelling along Muang Chaofa Road in Vichit, south of Phuket City, about 11.30pm on Friday night.
His death was reported at the hospital soon after noon today.
Mr Bates, a teacher at Baan Maireab School in eastern Phuket, did not recover consciousness.
The army-imposed curfew requires everyone to be off the roads before midnight throughout Thailand except in emergency or if catching a late flight.
According to an officer at Vichit Police Station, Mr Bates's motorcycle was travelling quite fast when it left the road surface and struck a tree, dislodging his helmet.
Relatives have been notified of his death.