Tihomer Stojic, 47, was detained in Buriram province on Thursday.
Officers allegedly found 20 grams of methamphetamine hidden in the glove compartment and back seat of the Australian’s car.
Simultaneous raids in Pattaya – a resort city near Bangkok dubbed “Sin City” for its high number of sex workers – saw fellow Australians Jamie Hansom, 46, and Steven Hovi, 58, arrested as well.
Their Thai girlfriends were also taken into custody as well as Nigerian Chimezie Duru, 38.
Police claim to have uncovered 1.1kg of meth at their respective homes, along with a gun, drug paraphernalia, mobile phone and bank slips showing transactions of more than 1 million baht (£25,000).
All three suspects are believed to be connected to the Hells Angels motorcycle gang, which is said to have become key players in the drug trafficking trade across Asia.
Police allege the gang were targeting tourists as meth customers.
Thai police are now on the hunt for Christoper Depp, a British national believed to be the head of the Pattaya drugs cell.
The group is believed to also have connections to the Comancheros, an Australian motorcycle gang which has also been implicated in drug trafficking as well as a high-profile murder in Auckland, New Zealand in 2018.
Two more Australian suspects are also being sought – Errol Stephen Gildea from Hell’s Angels and Amad Malkoun from the Comancheros.
Lieutenant General Montri Yimyam hailed the arrests as a significant breakthrough in the police’s battle against meth-dealing, and vowed that any criminals still at large would be brought to justice.
“There are many suspects all of different nationalities involved,” he told local media. “Our specialist team has made arrests and we will find the others involved.”
He said those already in custody would be interrogated to reveal information about the larger network.
Thailand’s notoriously harsh drug laws mean the suspects could face 25 years in prison or even the death penalty if convicted.