Thailand's first MotoGP since 2019 was delayed by heavy rain on Sunday as a torrential downpour hammered the Buriram circuit.
The race was originally supposed to start at 3:00pm (0800 GMT) but was put back 55 minutes.
There had been forecasts for heavy rain from Friday onwards, but conditions had been dry until race day Sunday and the earlier Moto2 event was disrupted.
Italian rookie Marco Bezzecchi is due to start in pole position for the MotoGP race with Spaniard Jorge Martin and title contender Francesco Bagnaia making up the front row.
Thailand has not hosted a MotoGP since 2019 because of Covid.