Somkiat Tangkitvanich, the TDRI president, said the low auction prices paid by the operators last week is no guarantee that customers will pay less for data services and voice mail as the regulator has requested.
The winners are not obliged to pass the savings on, and in any event the prices they paid for spectrum come from profits, not from service costs.
Mr Somkiat was testifying before a House committee on political development, mass communications and public participation yesterday.
Lower auction prices for operators simply means more profits for them, not necessarily a gain for consumers, he said.
"The auction price paid is part of their profit, not their cost," he said.
On Monday, the National Broadcasting and Telecommunications Commission (NBTC) urged the three auction winners _ AIS, Dtac and TrueMove _ to reduce charges for voice and data services by 15-20% before they can begin providing 3G services to consumers.
The regulator said savings for consumers resulting from the 20% cut would amount to 73.1 billion a year or more than 1 trillion baht over the 15-year life of the licences.
At the Oct 16 auction, Advanced Info Service (AIS) bid 14.6 billion baht, while Total Access Communications (Dtac) and True Corp bid 13.5 billion baht to win their licences.
The state made only 41.6 billion baht, only 2.78% more than the NBTC's combined minimum reserve price.
Mr Somkiat said the NBTC set the reserve price at 4.5 billion, or 70% of the actual frequency value, but the study conducted by a team of Chulalongkorn University economists suggested the 3G spectrum be valued at 6.44 billion baht for a 5MHz slot.
Suthiphon Thaveechaiyagarn, an NBTC commissioner, said the valuation price of 6.44 billion baht recommended by the Chulalongkorn University academics would have reduced the competition in the auction and the NBTC would have been criticised for setting too high of a price.
Meanwhile, NBTC secretary-general Thakorn Tantasit yesterday submitted a letter to the Department of Special Investigation asking it to probe the transparency of the 3G auction. He also handed over documents related to the auction to the DSI.
DSI chief Tarit Pengdith said this was the first time an agency, which is expected to face a probe, had wanted itself to be investigated by the DSI.
Mr Somkiat said the state and taxpayers would lose over 16 billion baht from the auction results. He said the three operators will pay only 900 million baht in licence fees annually over the 15-year licence period.
Mr Somkiat said AIS registered a net profit of 22.2 billion baht after paying a 24 billion baht concession fee to the state.
DTAC paid a 14 billion baht concession fee but still had 11.8 billion baht in profits remaining.
He said the telecom industry in Thailand still has only three operators because many obstacles block new operators from entering the market.