A Thai businessman caught poaching a rare black leopard plans to build a highway through a pristine forest in Myanmar that is home to endangered leopards and connects two tiger sanctuaries.

Conservationists, residents, and an armed ethnic group have all expressed concerns about the project.

"The very recent scandal, especially the president himself, caught red-handed poaching in the World Heritage site in Thailand … I think that raised a lot of scepticism about the governance of Italian-Thai," said Petch Manopawitr, deputy director of Indo-Burma for the International Union for the Conservation of Nature (IUCN).

Premchai Karnasuta is the president of Italian-Thai Development (ITD), a huge construction company.

Mr Premchai and three associates were caught camping in Thailand's Thungyai Naresuan Wildlife Sanctuary with guns, the skin of a black leopard and soup made from the female leopard's tail.

Police laid nine poaching and gun-related charges against Mr Premchai, and last week confirmed four tusks found subsequently at his house were from African elephants, therefore traded illegally.

The case has outraged many Thais, with fresh protests on Sunday in central Bangkok featuring demonstrators wearing black leopard masks demanding justice despite the tycoon's wealth and connections.

A rare black Indochinese leopard skin found in Premchai Karnasuta's possession. ( Supplied )

The high-profile poaching scandal has also rung alarm bells for conservationists and those effected by a proposed highway between the Thai border and Myanmar's Dawei special economic zone.

"We're really worried about the practice of Premchai … he's not following the law even in his own country, how he will follow the law in Myanmar?" said Thant Zin, director of the Dawei Development Association, an advocacy group in Myanmar.

Thant Zin says an access road built by Mr Premchai's company has already caused environmental damage.

"They should put the ITD in the blacklist," he told the ABC.

Short cut for trade, crossing for animals

The Dawei special economic zone is planned for Myanmar's west coast.

Once a 150km road is built linking it to Thailand, it will form a new trade route that avoids a long shipping journey around Malaysia, as well as a launching pad west to places like Dubai.

But the proposed two-lane highway will cut through Myanmar's Taninthariya forest - home to leopards, clouded leopards and black leopards, as well as Asian elephants, golden cats, marbled cats and bears.

According to WWF the Indochinese black leopard is rare, with about 900 to 2,500 still left in the wild. ( Supplied: Wildlife Conservation Society )

"It's one of the largest intact forest areas in South-East Asia and what's really unique about it is not only the wildlife that lives there but also how it provides a very important connection between the forest in Thailand and the forest in Myanmar," the World Wildlife Fund's (WWF) Hanna Helsingen told the ABC.

"This allows for species such as tigers and elephants to move on the landscape, to feed and mate, and disperse, which is critical for functioning ecosystems and the survival of these species."

The Western Forest complex in Thailand has the biggest population of wild tigers outside India and Nepal.

Further south lies another tiger-rich area — the Kaeng Krachan Forest Complex — with a strip of forest along the Myanmar border connecting the two sanctuaries.

"The landscape is one of the most important landscapes for tiger conservation globally," IUCN's Petch Manopawitr said.

The planned highway from the yet-to-be-built Dawei special economic zone to the Thai border could act as a barrier between these two tiger zones.

The Myanmar Government is pushing for a stronger environmental impact assessment (EIA) before giving the final green light.

"Biodiversity concerns or lack of mitigation for impacts on biodiversity have been cited as some of the main reasons for the EIA not being approved yet," Ms Helsingen said.

The road will also go through rural communities under the control of the Karen National Union (KNU), one of the many armed ethnic groups in Myanmar.

The KNU is demanding consultations with the Myanmar Government, or else risk breaching a 2015 ceasefire agreement.



Tunnels, bridges and canopies for wildlife

Most conservationists are resigned to the idea the highway will eventually be built.

But they said there was still hope of reducing the impact of the east-west road and allowing wildlife to keep using the forest as a "wild highway" north-to-south.

A map of Myanmar's pristine Taninthariya region. ( Supplied: Wildlife Conservation Society )

Animal scientists have teamed up with landscape architects at the University of Hong Kong to develop detailed plans that might help reduce roadkill, including 12 crossings at spots they think are migration paths.

"We've proposed adapting culverts to allow for wild cats to cross, we've proposed elevating part of the road which would produce an important elephant crossing," Mr Helsingen said.

"We've also suggested various barriers for light and noise which are important for birds, and canopy bridges in areas where we know there are primates such as gibbons, who really cannot cross a road by being on the ground, they have to be in the trees."

Of course, these wildlife-friendly features will cost more money.

However, WWF cites Italian-Thai Development's construction of wildlife overpasses on Thailand's Highway 304 as evidence animals can be worked into major infrastructure planning.

A representative from the ITD sub-company doing the project — the Myan Dawei Industrial Estate company — was not available for comment.

The Dawei project began in 2008 but stalled in 2013, with ITD citing financial difficulty.

Thailand's Neighbouring Countries Economic Development Cooperation Agency is currently considering a $180 million soft loan to Myanmar get things back on track.

The Japanese Government has also put money into the Dawei project and road surveys in the past.

"Including these measures from when roads are being built in the first place is always far cheaper than doing it later," Ms Helsingen said.

"We also make the argument that impacts of nature and people must be mitigated, so it should be considered part of the cost of building the road, either way."

With so much attention on Mr Premchai and his leopard poaching, ITD and financiers of the Dawei project face increased pressure to avoid killing more animals.