Transport Minister Prajin Juntong has insisted security checks at Suvarnabhumi airport did not find a gun and bullets in the luggage and carry-on bags of former Metropolitan Police chief Kamronwit Thoopkrachang on the day he left for Japan.
On Monday Pol Lt Gen Kamronwit was arrested at Narita International Airport in Tokyo with the weapon while attempting to board a plane back to Thailand.
The minister cited a preliminary probe into the record of security checks conducted on Pol Lt Gen Kamronwit at a VIP security checkpoint as well as his luggage and carry-on bags last Thursday before he took a Thai Airways flight to Japan.
National police spokesman Prawut Thawornsiri, meanwhile, said Pol Lt Gen Kamronwit had told Japanese authorities he unintentionally brought the gun to Japan with him from Thailand as he forgot the weapon was in his medicine box.
The medicine box was in his checked luggage when he travelled to Japan but was moved to his carry-on bag when he was in Japan, Pol Lt Gen Prawut said.
ACM Prajin said he had received a report from the board chairman of Airports of Thailand (AoT) that an investigation by the AoT showed no signs of a gun in Pol Lt Gen Kamronwit's luggage - neither the checked nor carry-on pieces - when he left for Japan.
The AoT reported to him that its investigation was conducted into both security checks on Pol Lt Gen Kamronwit's checked luggage and ones done at the VIP security checkpoint which he went through before he was allowed to board a plane last Thursday, said the minister.
Revenue Department director-general Prasong Poontaneat, in his capacity as AoT board chairman, said the airport's security camera footage showed that Pol Lt Gen Kamronwit cooperated fully with airport security staff when he went through security checks.
The AoT has also examined X-ray images of Pol Lt Gen Kamronwit's checked luggage and found no signs of the gun and ammunition Japanese police seized from him at Narita, Mr Prasong said.
This is a .22-magnum, five-shot revolver allegedly carried through Thai customs and around Japan by Pol Lt Gen Kamronwit Thoopkrachang. It is 11.75cm long, weighs 176 grammes, and the former Bangkok metropolitan police chief says he forgot it was in his medicine box.
AoT president Nitinai Sirismatthakarn said the CTX luggage scanners used at Suvarnabhumi are capable of detecting explosives, explosive compounds, bullets and even gunpowder residue.
Karn Thongyai, CEO and managing director of Asia Security Management Co which is responsible for security checks on checked passenger luggage at Suvarnabhumi, insisted the gun did not get through the checks carried out by the firm. An AoT source, however, said the CTX scanner was capable of detecting explosives and bombs only, not guns that are normally picked out by trained security-check staff.
A Government House source, meanwhile, said state security officials suspected the arrest of Pol Lt Gen Kamronwit was likely part of a plot to discredit Thailand's aviation safety image.
Pol Lt Gen Prawut said the gun and bullets seized from Pol Lt Gen Kamronwit on Monday were legal but it remained unclear as to what exact type they were.
Normally, prosecutors in Japan take at least 20 days to decide whether a suspect will be indicted, though in some cases, it takes only one or two days, he said.
"Japan has very strict laws on gun control and offenders can face a jail term of up to 10 years if proved guilty of violating these laws," he said.