Three Hong Kong men murdered in a gangland-style hit in Bangkok last Saturday were members of the 14K triad society, according to Thai police.
Detectives in the Thai capital said another underworld figure arrested earlier as part of a separate drug smuggling investigation identified the men as belonging to the group.
The development comes as Hong Kong police said they had received a formal request for help from Thailand through Interpol.
It is understood details of the dead men - Chen Jian-jun, 40, Chan Kam-yin, 41, and Hong Leung, 40 - have been passed to the SAR's Criminal Intelligence Bureau for background checks.
They were shot after their taxi was forced to stop on the overhead toll road near Don Muang International Airport. A fourth man travelling with them fled and is still missing.
It is not known if there were one or two gunmen.
