Police nabbed Weerasak Suksamdang, 26, in front of the TPI Polene building in Kaeng Khoi district and charged him with fraud and computer crime.
Weerasak denied the charges and was transferred to Muang Udon Thani Police Station, where complaints about the scam were filed on June 30.
The complainants said they were scammed by a Line group called “Vaccine Sinopharm”, which advertised jabs for 1,800 baht.
Police said the scammers claimed to be doctors who had procured leftover Sinopharm doses from the Federation of Thai Industries.
Once victims had transferred cash, they were deleted from the Line group and received no vaccine.
The scam netted over 300,000 baht from victims, police added.
The first suspected scammer, Ronakorn Puttaraksa, was arrested on July 2 in Muang Saraburi.
Police said Ronakorn confessed to setting up the Line group with Weerasak and others because he did not have a job.