The bidding time for next month's auctions of two licences on the 900-megahertz spectrum will be divided into two phases: 9am-9pm and midnight-6am.
Bidders will be allowed a three-hour break inside their auction rooms after the first 12-hour phase of bidding, due to start on Dec 15.
The National Broadcasting and Telecommunications Commission's telecom committee yesterday approved the new bidding rules, NBTC secretary-general Takorn Tantasith said.
He said the regulator had learned from the Nov 11 auctions for the 1800-MHz spectrum, which took 86 bidding rounds over 30 hours.
Those auctions ended with prices well exceeding expectations at a combined 80.9 billion baht.
Mr Takorn said the committee rejected bidders' requests to rest in a hotel rather than their auction rooms, as the regulator wanted to ensure transparency and prevent any possible collusion among bidders.
The NBTC is set to auction two licences on the 900-MHz spectrum, each for 10 MHz of bandwidth.
The bidding will start at 13.5 billion baht, increasing in 644-million-baht increments.
But if the price reaches 16.1 billion baht, bids will then increase in 322-million-baht increments.
The telecom committee yesterday also approved in principle setting the reserve price for further auctions next year at a level closer to the recent winning prices in the 1800-megahertz auctions.
The idea is to prevent bidders from winning with prices lower than those in the Nov 11 auctions.
The NBTC will in 2016 auction 45 MHz of bandwidth on the 1800-MHz spectrum now used by Total Access Communication Plc (DTAC).
DTAC signed a concession agreement with CAT Telecom to use the 1800-MHz spectrum to provide second-generation (2G) mobile service.
That concession is due to expire in 2018.
DTAC was one of two failed bidders in the marathon Nov 11 auction, with a final bid of only 17.5 billion baht.
"We'll set the reserve price and spectrum value of DTAC's 1800-MHz spectrum ourselves without relying on studies conducted by the International Telecommunication Union like in previous auctions," Mr Takorn said.
"We want to create an appropriate benchmark for future spectrum allocation."