Thailand's long-awaited auction of third-generation mobile phone licences could take place in the second quarter of 2010 rather than the first as suggested by regulators, two mobile phone operators said on Thursday.

Market leader Advanced Info Service ADVA.BK (AIS) and number two Total Access Communication DTAC.BK said they did not expect 3G to generate revenue in 2010.

Our 2010 business plan does not include 3G because we expect the 3G auction to take place in the second quarter, at the latest, AIS Chief Executive Wichien Mektrakarn told reporters at a seminar.

We are only focusing on 2G business and non-voice service for next year, he added.

Thana Thienachariya, Chief Commercial Officer of Total Access, said: The company does not expect revenue from 3G next year although the auction is likely to happen in the second quarter.

Earlier this month, the National Telecommunication Commission (NTC) said it hoped to hold the 3G auctions -- expected to generate around $1.2 billion for the state -- in the first quarter of next year.

However, the market is sceptical after repeated delays. Shares in telecoms operators have risen only 13.2 percent this year, underperforming a 52.4 percent rise in the main Thai index .SETI.

On Thursday, AIS shares fell 3.3 percent to 80.75 baht and Total Access eased 3.8 percent to 31.75 baht. Number three operator True Corp TRUE.BK sank 3.23 percent to 3.00 baht.

($1=33.11 Baht)

(Reporting by Manunphattr Dhanananphorn; Writing by Arada Kultawanich; Editing by Alan Raybould)