4, organisers said on Thursday.
The date change means that the Aragon Grand Prix in Spain will be brought forward a week to Sept. 27.
Thailand would have been the second round of the MotoGP season on March 22 but the race at the Chang International Circuit in the northeastern Buriram province was postponed on Monday.
Rossi announces decision to retire at end of season
The season-opener in Qatar scheduled for this Sunday has been cancelled, with only the second and third tier Moto2 and Moto3 categories racing. (Reporting by Alan Baldwin in London, editing by Toby Davis)
MotoGP star Jason Dupasquier dies after crash
Quartararo sets lap record to take pole at Italian GP