While national police chief Chakthip Chaijinda said investigators had identified the suspect who planted a bomb at the hospital, Srivara Ransibrahmanakul his deputy and head of the investigation, said he was far from a conclusion and only “20-per-cent satisfied”. Srivara said even a sketch of a suspect that was widely reported by the media, indicated nothing.

“I give a zero score for that sketch. After checking all the evidence we have, I would say that only 20 per cent is satisfactory,” Srivara said after a meeting with his team yesterday.

However, Chakthip said earlier the investigation had been able to identify a suspect, although he refused to divulge any other details. He said that investigators were checking if the suspect was the same individual who planted two other bombs near the National Theatre on May 15 and in front of an old government lottery building last month.

The hospital bombing, which injured 25 people, took place on the third anniversary of the coup. The explosion appeared to send a political message to the junta as it exploded in the Wongsuwan Room, named after Deputy Prime Minister Prawit Wongsuwan, who oversees security matters for the military government.

Contrary to Chakthip, Srivara said his team had no clue on the identity of the suspect. “Based on our information, I think it is not enough to seek any arrest warrants from the court,” he said. “Sometimes only crazy people come out to point a finger. We cannot rely on such information.”

More than 200 possible suspects had been suggested by many agencies, he said, noting that included more than 100 names from the Metropolitan Police and 80 to 90 from Special Branch. Different agencies had different information and none of it matched what others had, he said.

“The only thing I can say is that the bombers wanted to create chaos but I know neither their motivation nor political connection,” he said. “We don’t have enough information to suspect, let alone arrest, anybody.”

Srivara also said details disclosed recently from letters warning of a bomb and interrogation of hospital officials were useless, as they could not indicate anything about the bomb.

Asked if military personnel had interrogated some 40 to 50 people, Srivara said the police had not received such information from the military. He instructed his team to collect more evidence and information to make progress.

Commenting on speculation that fugitive red-shirt Wuthipong Kachathamkhun, alias Ko Tee, might have been behind the hospital blast, Chakthip said that investigators could not find clear evidence to implicate Wuthipong.

Chakthip said the deployment of over 200 police – with expertise and experience in bombing cases to handle inquiries into the three small blasts in Bangkok over recent weeks – was not an overreaction akin to “riding an elephant to capture a cricket”. Rather, it stemmed from the fact those behind the blasts operated in gangs.

Deputy Prime Minister General Prawit Wongsuwan, who appeared in public yesterday for the first time since the bomb, said authorities had questioned between 40 and 50 people, including staff, in the hunt for those involved.