Maverick Vinales led a Yamaha one-two in FP1 ahead of the inaugural MotoGP Thailand Grand Prix, with teammate Valentino Rossi 0.270 seconds adrift in second.
Marc Marquez took over at the top of the timesheets early on and remained there for almost the entirety of the session, with Vinales usurping him in the closings moments after a late time attack.
The Honda rider set the benchmark at 1:32.485s, some 2.7s off of teammate Dani Pedrosa's best lap from the test at Buriram in February, before improving to a 1:32.347s, and then a 1:31.970s to go 0.9s clear of Pramac's Jack Miller.
Miller's teammate Danilo Petrucci scythed Marquez's advantage down to 0.138s when he jumped up to second, before Andrea Iannone edged ahead by 0.005s on his Suzuki.
Marquez opened up his gap at the head of the timesheets to over three tenths with an improved effort of 1:31.739s, before Iannone reduced that once more to just 0.174s.
Marquez raised his gap to Iannone to 0.192s with 16 minutes remaining, and held that advantage at the top of the standings until the final two minutes.
Vinales was one of a handful of riders to run a fresh soft slick rear tyre at the end of the session, and used it to good effect to lift himself from sixth to the top with a 1:31.220s.
Teammate Rossi leaped up to second on a fresh medium rear having languished outside of the top 10 for much of FP1, while Ducati's Andrea Dovizioso was a further two tenths back in third.
Marquez as usual opted against a time attack late on and was shuffled back to sixth with his earlier effort of 1:31.668s, the Spaniard flanked by Miller and Tech3's Johann Zarco.
Iannone was seventh in the end from LCR's Takaaki Nakagami, Petrucci and Aprilia's Scott Redding, who confirmed earlier this week he will be departing MotoGP for the British Superbike Championship in 2019.
Thailand test leader Dani Pedrosa was a low-key 13th on the second of the Repsol bikes, while the injured Jorge Lorenzo made a steady start to proceedings on his Ducati in 17th and 1.3s off the pace.
A tenth further back came KTM's Pol Espargaro, who missed the Aragon race after re-breaking his collarbone in a practice crash, while World Superbike rider Jordi Torres brought up the rear of the filed in 24th as he continues to deputise for the injured Tito Rabat.
