KTM rider Pedro Acosta took a shock victory in a mesmerising Thailand Grand Prix MotoGP sprint after a last-lap penalty for Marc Marquez.

A crash for pre-race favourite Marco Bezzecchi opened the door to a ding-dong multi-lap duel between presumed Ducati 2027 team-mates Marquez and Acosta, which had to be decided by stewards' intervention.

Bezzecchi had led every session before the sprint, but faced an early challenge from Marquez after being beaten off the line. The Aprilia man struck back immediately at Turn 7, but Marquez overtook again at the final corner.

He then entered Turn 3 just a little wide and allowed Bezzecchi back through, only for Bezzecchi to crash out a handful of corners later at Turn 8 just as he was faced with a potential clear run to victory.

BEZZECCHI GOES DOWN 💥

CAN YOU BELIEVE IT?? 🤯#ThaiGP 🇹🇭 pic.twitter.com/BC20Xp2kBP

The crash could've made for a damp squib of a victory battle, but Acosta having overtaken Raul Fernandez for third at the opening lap set up a monster fight instead.

The same lap as Bezzecchi crashed, Acosta tried a last-lap move on Marquez but couldn't keep the line tight enough.

But Marquez never looked like shaking off Acosta. With the KTM consistently faster through the penultimate sector, Acosta attacked Marquez again and again at that final corner - on laps 7, 10 and 11, with Marquez beating him each time either immediately on corner exit or on the run down to Turn 1.

But when Marquez had a big Turn 5 moment on the penultimate lap, Acosta snuck ahead. And with it now Marquez's turn to attempt a last-corner divebomb, he forced Acosta well off the racing line - in a move that was immediately put under investigation and swiftly yielded a 'drop one position' verdict.

THE DIVEBOMBS OF ALL DIVEBOMBS 💣@marcmarquez93 sends @37_pedroacosta VERY wide 😱#ThaiGP 🇹🇭 pic.twitter.com/ZeiNaHzPUI

Ducati team boss Davide Tardozzi described the penalty as "unfair", while Marquez himself refused to give his opinion in parc ferme.

Marquez acquiesced with the stewards' verdict at the final corner of the race, giving Acosta his first-ever win in MotoGP.

Fernandez followed them across the line half a second back in third, while team-mate Ai Ogura made it a Trackhouse 3-4 after working his way up the order following a poor qualifying.

One of the riders Ogura made his way past was Jorge Martin, who made it home fifth on the road. However, Martin is at risk of an eight-second penalty due to a potential tyre pressure infringement.

Honda rider Joan Mir ran as high as fifth in the early going but slipped to seventh at the finish behind Brad Binder, though both Binder and Mir are potentially due to move up.

VR46 Ducati rider Fabio Di Giannantonio had podium pace but was run out wide by Alex Marquez at Turn 3 on the opening lap, both he and Marquez having to fight back.

Di Giannantonio's recovery ended with eighth on the road, capped off with an overtake on Pecco Bagnaia. Alex Marquez ended up 11th, right behind Luca Marini, who is in position to inherit a point if Martin is penalised.

Of the debutants, Diogo Moreira was a stellar 13th for LCR Honda, while Toprak Razgatlioglu was right there with the other Yamahas before a slow crash - from which he remounted to finish 20th.