Yesterday's attack comes 30 days after the capital was rocked by a series of explosions that killed three people and injured nearly 40 others on New Year's Eve - bombings that remain unsolved. All 19 suspects, most of them military officers, summoned by police investigators for questioning in connection with those attacks have already been released because of insufficient evidence.

Again, police investigators are likely to repeat the whole process and start by rounding up the usual suspects: "men in uniform" believed to be acting on behalf of "people who have recently lost power". These are euphemisms for rogue military or police officers who can be hired to commit any crime, and former prime minister Thaksin Shinawatra, respectively.

If the probe into the New Year's Eve blasts was any indication, investigators will again focus on the same theory that the perpetrators aimed to undermine the authority of the Surayud government and the CNS by terrorising the public and stirring up political disturbance.

Thaksin has categorically denied he had anything to do with the campaign of terror and complained that the Surayud government and the CNS were trying to discredit him by making such thinly-veiled accusations.

This time, because the target of the attack is a newspaper, investigators will also try to determine whether the motive behind the blasts was an attempt to intimidate Daily News because of its editorial stance or whether the perpetrators randomly selected the newspaper's offices.

One theory that was never considered by investigators is the possibility that some members of the CNS may have been involved in these acts of terror - a claim emphatically denied by military leaders.

The twisted logic in such a scenario - which remains unproven - holds that some military leaders may want to create a sense - real or imagined - that the country's fragile democracy needs to be protected by the armed forces. This dependency would give them the excuse they need to cling to power beyond the one-year deadline when full democracy is supposed to be restored and the military is to submit to the authority of a new democratically-elected civilian government.

As in virtually all bombings supposedly committed by people in uniform, the truth may never be known. A sad state of affairs that can be largely attributed to the military's outdated, but still widely-observed tradition, of protecting their own no matter what. The fact that too many officers of questionable character continue to be tolerated by the armed forces suggests that the system itself is not working.

The only way Surayud Chulanont, who retired as Army supreme commander, and the CNS can reclaim some of their credibility is for them to declare in no uncertain terms that the armed forces will not be exempt from the ongoing anti-corruption campaign. They must also make it clear that rogue officers who have been leading a criminal life or who have committed treasonable acts will not be allowed to hide behind the military institution's protective shield.

Its role in the overthrow of the corruption-prone Thaksin government, did not give the military - which is at least as susceptible to corruption as any other part of the state bureaucracy - a free pass to avoid public accountability and much-needed reform. Indeed as guardian of the country's security, the military must subject itself to the highest standards in terms of probity, integrity and professionalism. As honourable officers and self-appointed restorers of democracy, Surayud and CNS chairman General Sonthi Boonyaratglin must take the initiative to purge corrupt elements from the rank and file of the armed forces with the same intensity that they intend to carry out reforms in the Royal Thai Police force and state bureaucracy in general. Failing that, their credibility as leaders will be diminished and Thailand's future as an aspiring democracy will be greatly compromised.