BANGKOK (Reuters) - Thai junta leader Prayut Chan-o-cha will meet US President Donald Trump on Monday (Oct 2), marking an upgrade of ties between traditional allies that had become strained after a 2014 coup.

Washington was critical of General Prayut's May 2014 coup, which ousted a civilian government led by a populist premier, Ms Yingluck Shinawatra, and downgraded joint military exercises with Thailand. Some training, including the annual Cobra Gold military exercise, Asia's largest, continued on a smaller scale.

The White House meeting will underscore Mr Trump's willingness to embrace authoritarian leaders and regimes at the expense of human rights concerns, rights groups say.

Mr Trump welcomed Egypt's President Abdel Fattah al-Sisi earlier this year, drawing criticism from rights groups who say Gen Sisi has overseen a draconian crackdown on activists, something the Egyptian strongman denies.

Bangkok's ties with North Korea, Thailand's trade surplus with the United States and defence issues will be high on the agenda for the White House meeting, Thai government and senior Thai military sources told Reuters.

The visit will be an opportunity for the Americans to highlight North Korean business operations in Thailand after US Secretary of State Rex Tillerson urged Thailand to shut down North Korean businesses during a visit to Bangkok last month.

A senior military source, who declined to be named because he was not authorised to speak to the media, said Thailand will also discuss new defence purchase deals and finalise existing ones, including the delivery of four Black Hawk helicopters Thailand agreed to buy from the US before the 2014 coup.

Washington says it wants Thailand to take a diplomatic lead in the region in "freezing out" North Korea, which has an embassy in Thailand.

In response to US pressure, Thailand last month said trade between North Korea and Thailand had dropped by as much as 94 per cent this year.

But information on the ground paints a different picture.

Reuters visited seven businesses jointly or party owned by North Koreans out of 12 businesses listed in the Thai commerce ministry's business directory last month.

At least two people involved in those North Korean businesses who spoke to Reuters said there was no pressure from the Thai authorities. Another said indirect pressure meant he could no longer ship directly to North Korea.

All three declined to be named.

The Bank of Thailand has no policy to close down accounts owned by North Koreans in Thailand and an official at the central bank declined to comment about its regulations regarding North Korean-owned businesses and bank accounts.

The matter is a acutely sensitive for the Thai government, which last month denied that Mr Tillerson had raised North Korea during his Bangkok visit.

In August, Thai media reported that Gen Prayut had ordered news organisations to stop "digging" into North Korean businesses in Thailand. Gen Prayut's visit will be the first official visit by a Thai prime minister since 2005.

Thailand's military has banned protests, jailed critics and ramped up prosecutions under the country's strict royal insult law since toppling an elected government in 2014.

"Get ready for PM Gen Prayut to crow long and hard that this invite means he now has Washington's full seal of approval, and that Trump agrees with whatever comes next," Mr Brad Adams, Asia Director of Human Rights Watch, told Reuters. "Doubtless Trump fails to realise that this propaganda victory for Prayut... will come at the expense of the people of Thailand, who will pay for it in the form of intensified repression," said Mr Adams.

Major General Sansern Kaewkamnerd, a spokesman for the Thai government, declined to comment when contacted by Reuters about the US trip.

US pressure over the size of Thailand's trade surplus with the United States is also on next week's agenda.

Thailand was the United States' 25th-largest goods export market in 2016, but the US maintains an US$18.9 billion (S$25.66 billion) goods deficit with Thailand, the country's 11th largest.

Thailand's commerce ministry has said it hopes a narrowing trade gap would reduce the risk of Thailand being labelled a currency manipulator by Washington.

Gen Prayut and Mr Trump have at least one thing in common. Both have a history of lashing out at the media, with Gen Prayut infamously warning in 2015 that he has the power to execute reporters.

The visit also gives the outspoken former army chief a chance to burnish his leadership credentials amid signs he may be seeking to stay in power after an election tentatively scheduled for next year.