The 19-lap Moto3 race kicked off proceedings on Sunday at the Chang International Circuit, with Aspar rookie David Alonso scoring his fourth win of the season.
But the big story of the race was crash of title contender Ayumu Sasaki (Intact GP Husqvarna).
With Leopard Honda’s Jaume Masia finishing fourth, he has extended his championship lead to 17 points with three rounds remaining.
Alonso’s victory puts him firmly into title contention, 25 points adrift of Masia.
Honda Team Asia’s Taiyo Furusato was second, 0.266s behind Alonso, with Intact GP’s Collin Veijer completing the podium.
Behind Masia came Ajo KTM’s Deniz Oncu and Tech3 KTM’s Dani Holgado, who is also 25 points behind in the championship standings.
The top 10 was completed by Snipers Honda rider Matteo Bertelle, SIC58 Honda’s Riccardo Rossi, Aspar’s Rysuei Yamanaka and the second SIC58 bike of Kaito Toba.
Moto3 Thailand GP results
In the 22-lap Moto2 contest, Speed Up’s Fermin Aldeguer dominated by 3.4s over championship leader Pedro Acosta.
Home hero Somkiat Chantra completed the podium for Honda Team Asia, while Marc VDS’ Tony Arbolino was fourth to keep his slim title hopes alive.
Ajo KTM’s Acosta is now 63 points clear of Arbolino heading to the Malaysian GP next month.
Ai Ogura was fifth in Thailand on the second Honda Team Asia machine, from American Racing’s Marcos Ramirez and Ajo’s Albert Arenas.
Alonso Lopez was eighth on his Speed Up machine, with Aspar’s Izan Guevara and Yamaha VR46 Master Camp’s Manuel Gonzalez.