UPDATE: Marquez has been moved by ambulance from the circuit medical centre to Buriram hospital for further checks on his back and left leg.

Vinales fastest during opening practice for the Thailand MotoGP at Buriram, after a big accident for Marquez.

Marquez, who will be crowned world champion for an eighth time if he scores at least two points more than Dovizioso on Sunday, was quickest for most of the session but suffered a huge highside on his out-lap in the closing stages.

Marquez eventually limped slowly away before being taken to the medical centre in an ambulance...

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

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Thailand MotoGP - Free Practice (1) Results
1Maverick ViñalesSPAMonster Yamaha (YZR-M1)1'30.979s21/21326k
2Fabio QuartararoFRAPetronas Yamaha (YZR-M1)*+0.191s19/21326k
3Marc MarquezSPARepsol Honda (RC213V)+0.208s5/17330k
4Andrea DoviziosoITADucati Team (GP19)+0.226s20/20329k
5Jack MillerAUSPramac Ducati (GP19)+0.248s18/18328k
6Valentino RossiITAMonster Yamaha (YZR-M1)+0.503s20/22327k
7Franco MorbidelliITAPetronas Yamaha (YZR-M1)+0.590s20/22325k
8Danilo PetrucciITADucati Team (GP19)+0.614s17/18327k
9Joan MirSPASuzuki Ecstar (GSX-RR)*+0.774s21/22327k
10Francesco BagnaiaITAPramac Ducati (GP18)*+0.820s19/20326k
11Alex RinsSPASuzuki Ecstar (GSX-RR)+0.868s19/20327k
12Aleix EspargaroSPAFactory Aprilia Gresini (RS-GP)+0.886s17/17327k
13Pol EspargaroSPARed Bull KTM Factory (RC16)+0.916s20/20323k
14Takaaki NakagamiJPNLCR Honda (RC213V)+0.968s19/19325k
15Andrea IannoneITAFactory Aprilia Gresini (RS-GP)+1.260s17/19325k
16Tito RabatSPAReale Avintia Ducati (GP18)+1.301s21/21328k
17Miguel OliveiraPORRed Bull KTM Tech3 (RC16)*+1.545s15/15317k
18Cal CrutchlowGBRLCR Honda (RC213V)+1.575s13/19327k
19Jorge LorenzoSPARepsol Honda (RC213V)+1.859s19/19330k
20Mika KallioFINRed Bull KTM Factory (RC16)+1.898s9/23321k
21Hafizh SyahrinMALRed Bull KTM Tech3 (RC16)+2.054s16/18319k
22Karel AbrahamCZEReale Avintia Ducati (GP18)+2.150s17/17326k

* Rookie.

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