Police believe a suspect arrested for her alleged role in the March 7 hand-grenade attack on the Criminal Court is a key operative coordinating with a high-profile US-based suspect who has been financing an anti-government movement.
A senior police investigator said Suphaphorn "Dear" Mit-arak was coordinating with fugitive Manoon "Anek" Chaichana to plan attacks on five locations in Bangkok last month. Manoon is said to be living in San Francisco.
The two made contact through the chat application LINE and social media, and details were discussed with other operatives at a meeting in an area that comes under the jurisdiction of Chok Chai police, Pol Maj-General Chaiyaphol Chatchaidej said.
Both suspects had initially contacted Suraphol Iamsuwan, a self-proclaimed bomb maker, to carry out the first of five planned attacks. Suraphol later aborted his role, after receiving Bt15,000 (S$634).
This prompted Suphaphorn to turn to fugitive Wirasak Towangjorn, alias Yai Pattaya, who had contacted taxi motorcycle Mahahin Khunthong and hand-grenade thrower Yutthana Yenphinyo, the officer explained.
Police chief Pol General Somyot Poompanmuang later confirmed Suphaphorn's confession, saying details on the roles of each of the 16 suspects, including Manoon and Wirasak who are on the run, came from their own accounts.
He said Suphaphorn was a core leader of a political movement, which as of now cannot be named, and that her name was on a watchlist of security agencies - but there was no clear information about her activities until her role surfaced as a main coordinator in the hand-grenade attack.
The four other locations marked as sites for the attacks, according to Chaiyaphol, were Lumpini Park, an MRT station in Chatuchak, the 11th Infantry Regiment compound in northern Bangkok, and the Siam Kempinski Hotel car park.
A police source said later that Suphaphorn and Natthathida "Waen" Meewangpla - who was apprehended on Monday - face additional charges of planning bomb attacks as well as the charges of terrorism and criminal conspiracy, which have been pressed against all 16 suspects.
Natthathida, like Manoon, also faces lese majeste charges, the source said, without providing details on exactly what she did that violated the law.
Police spokesman Pol Lt-General Prawut Thawornsiri said police were seeking to bring Manoon back with Interpol's help to face terrorism charges. This is the first time that Thailand is seeking extradition of someone on terrorism charges.
Asked whether the hand-grenade attack would be considered a political case, which could result in the United States turning down the extradition request, Prawut said people with different political stances should seek solutions peacefully, not through violence or bomb attacks.