Spain's Jorge Martin won a thrilling Thailand MotoGP race Sunday to close the gap on Francesco Bagnaia in the world championship race.

Italy's Bagnaia crossed the line third behind Brad Binder but was awarded second place after the South African was demoted a place for exceeding track limits.

The trio had been involved in a titanic tussle over the closing laps with the lead exchanging hands before pole-sitter Martin pipped his rivals.

Bagnaia, attempting to defend his world title, has seen his championship lead cut to 13 points by Martin, who also won Saturday's sprint at the Buriram International circuit.

Martin had won the last five sprint races but not fared so well in the grands prix.

He crashed while leading in Indonesia a fortnight ago to gift Bagnaia the championship lead.

Then a disastrous gamble on a soft rear tyre last weekend in Australia saw the Italian extend his lead to 27 points as Martin finished fifth.

But the Spaniard closed the gap to 18 points with a dominant victory in Saturday's 13-lap sprint and then reduced it by another five points after winning the 26-lap main race by just 0.253 seconds.

The riders now head to Malaysia's Sepang circuit in two weeks' time with the championship duel looking likely to go to the wire.

The season rounds off in Qatar and Valencia next month.