* Vietnam unit of Thai Bev registers interest to buy stake
* Sources had said Thai Bev was seen as strong contender
* Global brewers also keen to buy into Sabeco -sources
* Sabeco auction is on Dec. 18 (Recast with Thai Bev statement)
HANOI/SINGAPORE, Dec 12 (Reuters) - Thai Beverage, through a Vietnam unit, has emerged as the only potential bidder which has registered to own at least 25 percent of the nation's top brewer, Sabeco, in which the government is selling a $5 billion stake, although no formal bid has been made.
Last month, Vietnam announced its biggest-ever and long-delayed state sale of Sabeco, or Saigon Beer Alcohol Beverage Corp, and said it was open to selling a stake of nearly 54 percent, but retained a cap of 49 percent on foreign ownership.
Citing people familiar with the matter, Reuters reported on Sunday that brewing groups including Thai Beverage, Anheuser-Busch InBev, Kirin Holdings, Asahi Group Holdings and San Miguel were interested in the auction.
The people had said that Thai Bev, controlled by tycoon Charoen Sirivadhanabhakdi, was shaping up as a strong contender, as it was familiar with the Vietnam system and saw Sabeco as key to expanding outside its home market.
"Thai Bev had been planning to buy into Sabeco long before the formal sales process kicked off. They seem to have ticked all the right boxes," a source, who declined to be identified as he was not authorised to speak to the media, said on Tuesday.
Thai Bev said late Tuesday that it had "confidence in the growth potential of the Vietnam market and has genuine interest in exploring investment opportunities in the country," but had not reached any agreement with Vietnam's trade ministry.
The matter is still under consideration by Thai Bev's local unit Vietnam Beverage Company Ltd, which has up to the last day of the bid registration process to decide whether to participate in the bidding, Thai Bev said.
On its website, Vietnam's trade ministry said Vietnam Beverage was the only investor to register an interest to own 25 percent or more of Sabeco as of 1100 GMT on Monday. It did not give any details.
Sabeco's shares jumped by the daily limit of 7 percent in early trade to stand at 313,000 dong ($13.8). The shares have nearly trebled since listing a year ago, with analysts citing a small float as inflating its market value.
The Sabeco auction is on Dec. 18, and bidders keen to own a stake of 25 percent or more of Sabeco's shares need to inform local authorities a week ahead.
Sabeco's foreign ownership cap limits overseas bidders to a minority stake of up to 39 percent, as foreign entities already own 10 percent.
Vietnam Beverage Company Ltd is owned by Vietnam F&B Alliance Investment Company, which is in turn 49 percent owned by BeerCo Ltd, an indirect wholly owned subsidiary of Thai Beverage, official documents on the companies showed.
Lack of control, the unorthodox manner of the sale of the Sabeco stake and sky-high valuations could put off some possible bidders, bankers, investors and lawyers said.
It was not immediately clear if other potential bidders for Sabeco had decided to bid for stakes of less than 25 percent or if they would sit out the auction.
Vietnam's trade ministry, which represents state shares in Sabeco, has said foreign investors can link up with Vietnamese firms to buy shares in Sabeco, but have to comply with local laws and regulations.
($1=22,710 dong) (Reporting by Mai Nguyen in HANOI and Anshuman Daga in SINGAPORE; Additional reporting by Chayut Setboonsarng in BANGKOK; Editing by Clarence Fernandez)