Wattana’s second wife, whose name has not been disclosed, reportedly met with the suspect at their condominium in Nonthaburi prior to each of the six incidents, the last of which took place last month at the Army-run Phramongkutkhao Hospital.

Wattana earlier told investigators he carried out the bombings alone due to his dislike of the military, which was heightened by the bloody crackdown on red-shirt protesters in 2010.

Investigators do not have evidence linking Wattana’s first wife to the multiple bombing incidents involving improvised devices, but said the woman, whose name was also withheld, worked at the Office of Army Commander-in-Chief prior to her recent retirement.

Sources said investigators were not yet convinced Wattana was a “lone wolf” in the incidents, three of which took place in 2007 and another three this year, even though he admitted to having planted the improvised bombs.

Wattana, 61, was an engineer who worked for the Electricity Generating Authority of Thailand and investigators said he had expertise in producing bombing devices with timers.

Besides the blast at Phramongkut-khao Hospital on May 22, Wattana said he had planted bombs at the former Government Lottery Bureau office and the National Theatre earlier this year, as well as other incidents in 2007 – in hope of discrediting the military-led governments.

Wattana told investigators he used public transport to take a bomb with a timer to the former office of the Government Lottery Bureau on Rajdamnoen Avenue before returning to his home in Nonthaburi.

Sources said the suspect was still insisting he committed the crimes to express his dislike of the junta-led Prayut government.

Meanwhile, sources said Wattana appeared to have owned only one bank account and there was no evidence of unusual money trails concerning the multiple bombing incidents.

Colonel Burin Thongprapai said the military had completed its interrogation of Wattana so the suspect would be handed over to police for further questioning.