Prime Minister Srettha Thavisin has ordered that a concerted effort be made to tackle bribery after a collapsed section of road in Bangkok was blamed on an overloaded lorry suspected of being approved as roadworthy due to illegal payments made to officials.
The truck apparently exceeded the weight limit but was still able to operate on busy Sukhumvit Road, causing damage to the road surface and resulting in two traffic accidents this week.
Mr Srettha was responding to speculation that a green star-shaped sticker with the letter B printed on it, spotted on the windscreen of the 10-wheel truck, is a symbol used by truckers so that police who have accepted bribes let them pass by without inspection despite being overweight.
The heavily loaded 10-wheeler broke a concrete slab placed over the opening to an underground cable trench in Phra Khanong district Wednesday morning.
The incident, which took place in the middle lane near Soi Sukhumvit 64/1, was the second after a previous incident occurred on Ratchaprarop on Tuesday.
Wednesday's misadventure left two other drivers injured while Tuesday's incident resulted in an SUV and its driver being stranded in a hole on the road surface that opened up immediately after the truck passed over it.
The Ministry of Transport, Bangkok Metropolitan Administration (BMA) and the Department of Highways will work together to look into the problem of illegally loaded trucks and find ways to prevent any such incidents from recurring, Mr Srettha said.
The Metropolitan Police Bureau (MPB) has launched a probe into whether the 10-wheeler was to blame on Wednesday if bribes were involved, and the meaning of the suspicious sticker, Pol Col Witthawat Chinkham, acting commissioner of MPB Division 5, said on Thursday.
A fact-finding committee was formed on Wednesday to investigate the excess weight the truck is believed to have been carrying, and whether any corruption was involved, he said.
Pol Gen Torsak Sukvimol, the national police chief, said there should be sufficient evidence to support claims the police were bribed to turn a blind eye if there are grounds for them, as such accusations have damaged the police force's reputation.
As of late Thursday, it remained unclear whether the green sticker can be said to serve as evidence that bribes were paid to the police, he said, adding that wrongdoers would face legal and disciplinary action.
Meanwhile, Apichart Pairoonrueng, president of the Land Transportation Association of Thailand (LTAT), confirmed the green sticker effectively gives heavy trucks a "free pass" when it comes to exceeding the weight limit and operating in the city outside of the allowed hours.
Without such a sticker, these trucks could never pass through several intersections where the police usually have checkpoints, he said.
Mr Apichart said the green sticker allows trucks to carry dirt to and from construction sites across Bangkok without having to worry about any police interference.
It is awarded in exchange for bribes to the police and BMA officials, he added.
As for the letter B being linked to an affluent individual with the nickname Big, as people online have speculated, Mr Apichart said he had never heard the moniker before.
As a member of the House sub-committee on bribery investigation, he will hand over all of the information at his disposal to the subcommittee's chairman, he said.
The BMA lacks a weighbridge of its own for lorries and trucks, he said.