Human rights groups have called on the British foreign secretary, Dominic Raab, to intervene over the detention of three young environmental activists when he meets Cambodian leaders on Wednesday in efforts to build trade ties between the two countries.

The activists, who were arrested at the weekend, face up to 10 years in jail for insulting the Cambodian king. Their case has been raised by environmental activist Greta Thunberg and NGO groups in the country.

Raab is due to meet the Cambodian foreign minister, Prak Sokhonn, to set out the UK’s bid for “Asean [Association of South-east Asian Nations] dialogue partnership” status before Cambodia takes up the chair of Asean next year. The UK is trying to expand its trade and security ties in south-east Asia in the wake of Brexit, but will also be pressing Asean to take a more interventionist stance on the crisis in Myanmar.

It is the first visit to Cambodia by a British foreign secretary for 30 years.

Ruos Sarat of the Cambodian Centre for Human Rights told the Guardian: “We want the foreign secretary to use his diplomatic influence to say these young people should be praised and not silenced. Britain is the chair of the UN conference on climate change, and we hope the foreign secretary will defend those who are trying to defend the Earth’s climate. The three face up to 10 years in prison if found guilty of plotting, and up to five years in jail for royal insults. One of the four originally arrested has been released.”

The dilemma posed by the pressure from the rights groups is typical of the kind that the UK will face in the years ahead as it seeks to strengthen economic ties with countries that often do not match western values.

The three detained activists, from a group called Mother Nature, are Sun Ratha, 26; Ly Chandaravuth, a 22-year-old law student; and Yim Leanghy, 32. They were arrested on 16 June in Phnom Penh’s Daun Penh district. The group had filmed sewage pouring from the royal palace into the Tonle Sap River.

The Cambodian government claims that the group is seeking to topple the regime and is foreign funded.

A joint statement issued by community groups on the eve of Raab’s visit said: “Authorities should stop imprisoning and start listening to our youth activists who are on the front line of documenting the risks Cambodia faces from natural resource exploitation and environmental degradation. These activists are tirelessly and selflessly working for the nation’s best interests.”

The arrests come less than two months after the conviction of three other Mother Nature activists for baseless charges of incitement, the statement claims.

The deputy director of Human Rights Watch Asia, Phil Robertson, said: “Foreign governments, the United Nations country team, and international donors should call on the Cambodian authorities to drop their absurd charges against the environmental activists and publicly condemn any further clampdown on peaceful activism.”

A spokesperson for the British Foreign Office said: “The UK is committed to promoting freedom of expression, and the charges brought against these three climate activists are concerning.”

The US ambassador to Cambodia, Patrick Murphy, wrote on Twitter on Monday that he was “very troubled to hear of the arrests of more environmental youth activists. Documenting pollution is a public service, not terrorism. We urge authorities to be responsive to its citizens, not to silence them.”

In a statement last Thursday, the US embassy in Cambodia said it was ending its aid programme aimed at protecting one of the country’s biggest wildlife sanctuaries, citing worsening deforestation and the silencing of those who speak out against the destruction of natural resources. Cambodia said the deforestation and illegal logging had been brought to an end.

Cambodia has been severely criticised by the UN for corruption, its treatment of trade unionists, and repressive media laws.