"Small patrol group"
References to the RKK, which means the "small patrol group" in Malay, first surfaced in a Bangkok Post report in January 2006.
The report described the RKK as one of several fighter groups operating in the provinces near the Malaysian border.
The paper said the group used the home of a Muslim teacher called Amran Masor in Thailand's Pattani province as a training base.
More than 2,000 people have been killed in three years of separatist unrest in the three southernmost provinces of Narathiwat, Yala and Pattani.
The areas are populated mainly by ethnic Malay Muslims and were annexed by Buddhist Thailand a century ago.
Dozens of bombs exploded across the region on Sunday evening, killing eight people and wounding 50 in attacks that coincided with the start of lunar New Year celebrations.
The day after the blasts, the army-appointed government in Bangkok admitted it had no idea who the culprits were.