Meanwhile, Collective Action against Corruption (CAC), a network of more than 500 companies, issued a statement praising organisations which helped to upgrade corporate governance.

Sorrayuth quit his TV shows on Thursday evening after major advertisers stepped up pressure by suspending their support for his Channel 3 programmes, which account for about 4 per cent of the station’s revenue.

Channel 3 is operated by BEC World, which has annual revenues of more than Bt16 billion.

Total Access Communications (DTAC), the country’s second largest mobile phone operator, and the Tourism Authority of Thailand were among major spenders which suspended ads on Sorrayuth’s shows in the wake of the Criminal Court finding him and others guilty of bribery in a ruling on Monday.

The CAC said the hundreds of large companies it had grouped together fought corrupt practices, including bribery, with the objective of promoting good corporate governance and social responsibility.

Mongkolkit Suksintharanon, secretary-general of Anti-Corruption Network, said the organisation wanted the AMLO to examine the accounts of Sorrayuth’s company Rai Som, as well as its advertising contracts with state agencies dating back to 1996, which was before Sorrayuth joined Channel 3.

The court ruled that bribes had been paid involving Rai Som and the Mass Communication Organisation of Thailand’s Channel 9, resulting in damages of Bt138 million to the state agency.

The court sentenced Sorrayuth to a jail term of 13 years and four months, while two other people also face jail over the scandal. Sorrayuth said he would appeal.

Mongkolkit said the AMLO needed to investigate other contracts between Rai Som and the MCOT, as well as the related money trails.

The AMLO said there was no need to confiscate assets if Rai Som had already returned the money it owed MCOT.

Chatchai Phayuhanawichai, director of the Government Savings Bank, said the bank had suspended its advertising for Sorrayuth’s programmes since 2012 after it got a directive on good corporate governance, but continued to advertise on other Channel 3 programmes.

Prior to Sorrayuth’s decision to call it quits, the CAC issued a statement urging its member organisations to join forces after Sorrayuth continued to host his TV shows following Monday’s verdict.