Attracted by growing beer consumption in Vietnam as domestic sales decline, Thailand’s top brewers have made approaches to purchase a stake in Saigon Beer Alcohol Beverage Corp., people with knowledge of the matter said.

Thai Beverage PCL, the maker of Chang beer, is seeking to buy about 40% of state-owned Saigon Beer Alcohol Beverage, the people said, in a deal that could cost it close to $1 billion.

ThaiBev has offered to pay as much as 80,000 Vietnamese dong ($3.76) a share for the company, which is also known as Sabeco. This translates to about a 60% premium to the Vietnamese company’s over-the-counter price of 45,000 dong to 50,000 dong a share, said a senior government official in Vietnam’s Ministry of Trade and Industry.

The price values Sabeco, which is 89%-owned by the government, at roughly $2.4 billion.

The official also said Thailand’s Singha Corp., which makes Singha Beer in addition to snack foods, has also expressed interest in buying the government’s Sabeco stake. The official didn’t provide details on Singha’s offer for Sabeco. The approaches by Singha and ThaiBev were unsolicited, as the government hasn’t officially put any of its stake on the block.

ThaiBev and Singha declined to comment.

The official said ThaiBev executives had already met with Vietnam Minister of Industry and Trade Vu Huy Hoang with regard to interest in Sabeco. The minister, the official said, advised ThaiBev to speak to Sabeco Chairman Phan Dang Tuat, adding that a decision to begin sale talks will depend on Prime Minister Nguyen Tan Dung.

Mr. Tuat, the official said, hasn’t agreed to meet ThaiBev yet.

Mr. Tuat, meanwhile, said in an interview that any plans to sell the government’s stake would be up to the state, but added that if it bought 40% of Sabeco, ThaiBev would be breaching existing foreign-investor limits of 25% on state assets.

He declined to comment further.

Vietnam is attractive to foreign investors because of growth prospects in its beer market.

Euromonitor data shows that beer volumes in Thailand were estimated at 1.93 billion liters last year, down from 1.97 billion liters in 2013. In Vietnam, volumes rose 8% last year to 3.2 billion liters, according to data from the Ministry of Industry and Trade. Euromonitor expects beer volumes in Vietnam to grow 9% this year to 3.88 billion liters, while it expects Thai volumes to drop to 1.89 billion liters in 2015.

Sabeco, which sells brands including 333 and Saigon beer, controls nearly 46% of Vietnam’s beer market. If the stake sale occurs, it would be the latest in a string of Vietnamese government privatizations aimed at reforming state-owned enterprises.

ThaiBev is owned by Thai tycoon Charoen Sirivadhanabhakdi, who according to Forbes had a net worth of $11.3 billion at the end of June. He also has interests in nonalcoholic drinks and real estate. The Singha Beer brand was built by the Bhirombhakdi family, who opened the country’s first brewery in the 1930s.

Sabeco posted a net profit of 2.73 trillion dong for the first nine months of last year, up 23% from a year earlier.

In the past, the Vietnamese government planned to sell its stake in the brewer to strategic investors. These plans were delayed because of various procedural issues.

ThaiBev’s interest in Sabeco follows a collapsed deal to buy a Myanmar brewer owned by another of Mr. Charoen’s companies, Fraser & Neave Ltd. The acquisition of a stake in Sabeco would open up an alternative emerging market to Mr. Charoen, who has been on an aggressive shopping spree during the past few years in the property and consumer sectors. Mr. Charoen bought Fraser & Neave for $11 billion in 2011.

By Vu Trong Khanh & P.R. Venkat - The Wall Street Journal - February 3, 2015