Suwit Mingmol, the union's chairman, submitted on Friday a letter to M.L. Panadda Diskul, who supervises the 77.28% state-owned MCOT, the operator of ModernineTV station, 62 radio stations and the Thai News Agency.
"The letter shows our support for the NCPO (National Council for Peace and Order)'s corruption tackling policy," said Mr Suwit.
"As many of MCOT's directors are resigning, we've taken this opportunity to show our strong support for the NCPO's move to appoint a new board to replace the existing one. We're also urging the incumbent to bow out as soon as possible since it couldn't reach a decision on the digital TV project, causing damage to the MCOT," he added.
He claimed MCOT's employees from the operational level to executive vice presidents also supported a move to use MCOT as a model in tackling corruption and realise the NCPO's policy.
An MCOT source said after the union's move today, an acting senior vice president banned the reporting of the union's move.
The union, however, will submit a similar letter to NCPO chief Gen Prayuth Chan-ocha on Monday.
M.L Panadda, who is also deputy permanent secretary of the Interior Ministry, said he would look into the facts, especially those lacking transparency, and take appropriate action.
MCOT shares closed Friday's morning session unchanged at 26 baht in trade worth 1.77 million baht.