Quartararo back on top during a dry FP4 at the Thai MotoGP, after fitting a new soft rear tyre to leapfrog ahead of Marquez at the end of the session.

Marquez, who will be crowned the 2019 MotoGP champion if he scores at least two points more than Dovizioso on Sunday, required a trip to hospital for checks on his leg and back after a Friday morning highside before returning in FP2.

KTM's Espargaro is returning from a left wrist fracture at Aragon.

Qualifying 1, for those outside the top ten after third free practice, will now get underway.

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Thailand MotoGP - Free Practice (4) Results
1Fabio QuartararoFRAPetronas Yamaha (YZR-M1)*1'30.755s16/16328k
2Marc MarquezSPARepsol Honda (RC213V)+0.027s9/16327k
3Maverick ViñalesSPAMonster Yamaha (YZR-M1)+0.198s14/17325k
4Jack MillerAUSPramac Ducati (GP19)+0.498s5/15330k
5Andrea DoviziosoITADucati Team (GP19)+0.634s15/15328k
6Valentino RossiITAMonster Yamaha (YZR-M1)+0.656s13/16325k
7Alex RinsSPASuzuki Ecstar (GSX-RR)+0.672s11/15327k
8Franco MorbidelliITAPetronas Yamaha (YZR-M1)+0.716s12/17325k
9Pol EspargaroSPARed Bull KTM Factory (RC16)+0.717s12/14326k
10Danilo PetrucciITADucati Team (GP19)+0.740s13/14332k
11Joan MirSPASuzuki Ecstar (GSX-RR)*+0.772s14/17326k
12Francesco BagnaiaITAPramac Ducati (GP18)*+0.855s13/14327k
13Cal CrutchlowGBRLCR Honda (RC213V)+1.025s16/16324k
14Andrea IannoneITAFactory Aprilia Gresini (RS-GP)+1.271s12/15323k
15Aleix EspargaroSPAFactory Aprilia Gresini (RS-GP)+1.370s5/12324k
16Takaaki NakagamiJPNLCR Honda (RC213V)+1.377s13/17323k
17Hafizh SyahrinMALRed Bull KTM Tech3 (RC16)+1.480s16/16321k
18Mika KallioFINRed Bull KTM Factory (RC16)+1.489s16/16322k
19Miguel OliveiraPORRed Bull KTM Tech3 (RC16)*+1.539s7/15320k
20Tito RabatSPAReale Avintia Ducati (GP18)+1.616s11/15327k
21Karel AbrahamCZEReale Avintia Ducati (GP18)+2.042s11/12326k
22Jorge LorenzoSPARepsol Honda (RC213V)+2.139s5/13325k

* Rookie.

Fastest Friday Time:
Fabio Quartararo FRA Yamaha 1m 30.404s (FP2)

Official Buriram MotoGP records:
Best lap:
Marc Marquez SPA Honda 1m 30.031s (2018)
Fastest race lap:
Marc Marquez SPA Honda 1m 31.471s (2018)

By Peter McLaren