Factbox-Who are the main candidates for Thailand's next leader?

BANGKOK (Reuters) - Political parties in Thailand have until Friday to submit the names of their prime ministerial candidates ahead of a May 14 general election.

The contest will showcase a long-running political battle between the billionaire Shinawatra family and its business allies and a conservative pro-military establishment.

The next premier will be decided by the end of August at a bicameral sitting of the new Thai parliament and appointed senate. Here are some of the contenders.

PRAYUTH CHAN-OCHA

The incumbent has led Thailand for nearly eight years since he ousted a civilian government in a 2014 coup while army chief.

He was elected prime minister in 2019 and if chosen again by lawmakers, he can only serve half of the four-year term as he will have reached the maximum eight years permitted.

Prayuth, 69, has been unpopular in national opinion polls with 16.3% support in a Super Poll survey last week and is running with the new, conservative United Thai Nation Party.

PAETONGTARN SHINAWATRA

The youngest child of the former, but still popular, premier Thaksin Shinawatra, Paetongtarn, 36, has consistently topped surveys, with a March poll putting her support at 32.1%.

She has been campaigning in the vote-rich rural strongholds of the main opposition Pheu Thai party, promising to bring back populist policies like nearly doubling the daily minimum wage to 600 baht ($17.61).

Best known by her nickname, "Ung Ing", Paetongtarn is an executive at a real estate firm and the biggest shareholder in another developer, SC Asset. She is currently pregnant, due to give birth just a few weeks before the election.

PITA LIMJAROENRAT

The 42-year-old is leader of the progressive opposition Move Forward party - the only one pushing for amendments to Thailand's strict royal insult law that punishes offenders with up to 15 years in jail.

His other policies include promoting small businesses, curbing monopolies and ending military conscription. The party's supporters are mostly younger voters.

PRAWIT WONGSUWAN

A seasoned political dealmaker and current deputy premier, Prawit, 77, is a nominee for prime minister for the Palang Pracharat party following ally Prayuth's departure. He is a staunch royalist from the same military clique as Prayuth, and served in his junta.

He has positioned himself as a candidate who can bridge the divide between conservatives and democratic forces.

ANUTIN CHARNVIRAKUL

Health Minister Anutin oversaw COVID-19 lockdowns, treatment and vaccine procurement and was criticised for calling it "just a flu". He has been praised for restarting tourism through a vaccinated travel programme.

His Bhumjaithai party controls about 50 seats in parliament and successfully delivered on a 2019 campaign promise to decriminalise and promote medical cannabis. However, that led to a rise in recreational use, upsetting conservatives and prompting Anutin, 56, to take a tougher stance against other drugs.

JURIN LAKSANAWISIT

Jurin, 67, of the Democrat Party is seen as part of the conservative establishment. The party has lost support in recent years because of defections and Jurin aims to revitalise it as it competes for the traditional conservative vote in the south and Bangkok.

SRETTHA THAVASIN

Srettha, 60, quit his job as the chief executive of luxury real estate developer Sansiri Pcl on Tuesday. He is widely expected to be named a prime minister candidate for Pheu Thai. His name on the ticket, analysts say, balances out Paetongtarn's perceived inexperience. Srettha is known for sharing his views on Twitter and is popular with the business community.

(Reporting by Chayut Setboonsarng and Panarat Thepgumpanat; Editing by Kanupriya Kapoor, Martin Petty)