The Australians have been named as John Edward Cohen, 33, and Adam Lewis Shea, 26.
Police are keen to establish whether the pair have links to the notorious Bandidos gang, reported to have been expanding from Australia to Phuket.
Some gang paraphernalia has been found, police said today.
However, a caller to Phuketwan said the motorcycle club involved was the Rebels MC.
Initial reports say that Cohen, the man who allegedly fired the shots that wounded Johann Baschenegger, 41, and Joseph Woerner, 71, actually intended to shoot a Danish man in a dispute about a motorcycle.
According to police, Cohen fired the Ruger P345 near the Baan Pirin Hotel about 7.45pm in Soi Sansabai. He then handed the weapon to Shea, the police say, and the men ran in different directions.
Cohen was arrested in the OTOP bar sector off Rat-U-Tit 200 Pi Road. Shea is alleged to have hid the handgun in a plastic bag before being arrested at the Aussie Bar in Soi Bangla.
The men were being interviewed by officers at Kathu Police Station, which oversees the Patong region, today.
The unintended victims are in Patong Hospital. Mr Woerner had just arrived on Phuket while Mr Baschenegger had been holidaying for about a month, police said.
Cohen is a long-term expat who owns a hotel in Patong, police said.