Flight lieutenant Kanok Thong-purk, a THAI executive vice president, said the result of the investigation would be known within 30 days.

Thailand is among seven countries named by the United Kingdom’s Serious Fraud Office (SFO), which found conspiracy to corrupt or failure to prevent bribery by Rolls-Royce, involving payment of US$18.8 million (Bt663 million) to regional intermediaries.

“Some of the money was for individuals who were ‘agents of the State of Thailand and employees of Thai Airways’,” the SFO said. These agents “were expected to act in Rolls-Royce’s favour with respect to a purchase by Thai Airways of T800 engines”, the BBC reported.

British daily The Guardian reported that the firm paid more than $36 million between 1991 and 2005 to agents to help it secure three separate contracts to supply Trent aero engines to Thai Airways.

Rolls-Royce (Thailand) refused to comment on the accusations yesterday.

The SFO revealed 12 counts of conspiracy to corrupt or failure to prevent bribery also in six other countries – Indonesia, India, Russia, Nigeria, China and Malaysia. Rolls-Royce employees allegedly paid bribes to middlemen and foreign officials to win bids from 1989 to 2013.

The aerospace company made the admission on Tuesday at the high court in London, a day after it was revealed that it would pay 671 million pounds in penalties to settle nearly 25 years of corruption allegations.

The payment will comprise 479 million pounds (Bt29.1 billion) plus cost to the UK’s SFO, 141 million pounds to the US Justice Department, and another 21.5 million pounds to Brazilian regulators.

The long-running corruption case is considered the biggest individual investigation conducted by the SFO.

The probe revealed “the most serious breaches of the criminal law in the areas of bribery and corruption”, the judge said in a written judgement issued at Southwark Crown Court in central London.

However, Rolls-Royce was allowed the deferred prosecution agreement (DPA) with the SFO, which was approved by the court on Tuesday. Under the agreement, organisations are allowed to pay penalties with avoidance of prosecution if they confess to economic crimes such as fraud or bribery.

Following the settlements being reached, Rolls-Royce chief executive Warren East apologised for the misconduct uncovered during the investigations launched in 2012.

“The behaviour uncovered in the course of the investigations by the Serious Fraud Office and other authorities is completely unacceptable and we apologise unreservedly for it,” he said in a statement.