Suthiphon Thaveechaiyagarn, the National Broadcasting and Telecommunications Commission (NBTC) commissioner, told the Bangkok Post the NBTC was waiting for the court's ruling on whether to issue an injunction - initially expected yesterday.
However, the ruling is now expected to be made on Monday.
Mr Suthiphon said if the court throws out the request for an injunction by telecom analyst Anuparp Thiralarp and the Consumer Rights Protection Association, it will force other potential petitioners to review their petitions.
A dismissal of the request would enable the auction to proceed as planned on Tuesday.
He said the NBTC has considered counter-suing Mr Anuparp over what it believes is an ulterior motive in seeking to stifle the auction if the Administrative Court dismisses the petition on Monday.
Mr Suthiphon said Mr Anuparp should have pursued court action back in August when the auction was announced.
Rebutting criticism the auction has attracted too few bidders, he explained legal restrictions made it possible for only three firms to enter the race.
The three qualified bidders are Advanced Wireless Network, a subsidiary of Advanced Info Service; DTAC Network, a subsidiary of Total Access Communication; and Real Future, a subsidiary of True Corporation.
Mr Suthiphon also dismissed criticism from Somkiat Tangkitvanich, president of the Thailand Development Research Institute, that the reserve price of each of nine spectrum slots put up for auction worth 4.5 billion baht was too low. Each slot contains five megahertz of bandwidth.
The commissioner said a NBTC-commissioned study by economics experts at Chulalongkorn University estimated the value of each slot at 6.4 billion baht.
However, the study suggested the NBTC set the reserve price of each slot at 67% of the actual value of 6.4 billion baht, or 4.3 billion baht.
The study put forth the 67% figure which was realistic and would attract interested buyers.
Mr Suthiphon said in fact, the 4.5-billion-baht price tag was even higher than the study-suggested reserve price.
If the price was set too high, the auction might not draw any bidders. If the country continues without the 3G system any longer, it could amount to losses of up to 70 billion baht a year, he said.
Meanwhile, a civil group coalition will next week lodge a petition with the Administrative Court seeking the auction's suspension, said Suriyasai Katasila, coordinator for the Green Politics group.
Mr Suriyasai said the coalition will also ask the Administrative Court to order the NBTC to raise the reserve price.
He said the coalition does not oppose the auction per se but if it is to take place it must proceed transparently and leave no room for price collusion.
The petition will be filed on Monday, on the eve of bidding day, he said.