The National Broadcasting and Telecommunications Commission (NBTC) is expected to revoke the licences of cash-strapped Thai TV Co's two channels without further notification next Monday.
Secretary-general Takorn Tantasith said the regulator had offered the company many chances to solve its financial problems.
Thai TV failed to pay the second instalment of its auction fee last May.
Its two digital channels, Loca and Thai TV, went off the air on Dec 1, and the regulator suspended the licences for 90 days until yesterday, which was also the new deadline for Thai TV to pay the overdue second instalment.
The second instalment amounts to 288 million baht plus 7.5% interest.
Acting deputy secretary-general Sombat Leelapata said the NBTC's broadcasting committee would decide whether to revoke the licences for the two channels.
Thai TV president Pantipa Sakulchai could not be reached for comment.
After the licence revocation, Thai TV must pay the remaining auction fees plus interest totalling 1.63 billion baht.
If necessary, the NBTC will send a formal letter to Bangkok Bank, the issuer of the bank guarantee for Thai TV, requesting payment on behalf of the ailing company within 30 days.
Suchart Chomkul, a legal adviser to Thai TV, earlier said Ms Pantipa wanted to end her digital TV business and would not pay more auction fees to the regulator.
Thai TV sent a letter to the NBTC showing a strong intention to return the two channel licences and end digital TV operations.
The company faces 300 million baht in losses from running the two channels.
Mr Suchart said if the NBTC sent the letter to Bangkok Bank asking for money on behalf of Thai TV, the company would file a request for an emergency injunction with the Central Administrative Court against the forced payment.
Last June, Thai TV sued the NBTC at the court for failing to facilitate a smooth transition to digital TV, asking for 713 million baht in compensation.