A bitcoin investor couple are on the run and facing potential death sentences after Thai authorities alleged their life on the open seas was a threat to national sovereignty.

Key points: Seasteading promotes living in international waters to be free of any nation's laws

Seasteading promotes living in international waters to be free of any nation's laws Thailand's navy claims the couple endangered national sovereignty, an offence punishable by death

Thailand's navy claims the couple endangered national sovereignty, an offence punishable by death The couple went on the run before the authorities raided their floating home

United States citizen Chad Andrew Elwartowski and Thai national Supranee Thepdet, who goes by the English name Nadia Summergirl, had been living part-time in a small structure anchored outside Thailand's territorial waters, about 12 nautical miles (22 kilometres) from Phuket's shore.

But the couple fled ahead of Thai authorities raiding their floating platform home in the Andaman Sea, where the couple sought to pioneer the "seasteading" movement.

Supranee Thepdet, left, and Chad Elwartowski sought to be pioneers of the seasteading movement, which promotes living in international waters free of any nation's laws. ( Facebook: The Seasteading Institute )

Seasteading promotes living in international waters to be free of any nation's laws.

The "seavangelists" believe floating nations will "restore the environment, enrich the poor, cure the sick, and liberate humanity from politicians".

But Thailand's navy claims the couple endangered national sovereignty, an offence punishable by life imprisonment or death.

The police complaint alleged the couple breached section 119 of the Thai criminal code, which refers to the intent to impact the sovereignty or deteriorate the independence of the state.

"The complaint has been filed against them for breaching Section 119 of the Criminal Code as there is evidence showing that they have publicly invited people on social media to stay at the site, which is adjacent to our territorial waters … we have laws to deal with this. It affects our sovereignty," said the Third Naval Area commander, according to the Bangkok Post.

"This is ridiculous. We lived on a floating house boat for a few weeks and now Thailand wants us killed," Mr Elwartowski wrote on Facebook.

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Ocean Builders, which is connected to the seasteading movement, said in a statement that "Chad and Nadia are safe for now but understand that Thailand is currently being run by a military dictator".

The statement claimed a fair trial for the duo was unlikely.

"We hope this issue can be resolved diplomatically with the Thai government and are ready to talk to anyone in charge at any time," Ocean Builders said.

"We have tried several times to talk to anyone but were always told that we have nothing to worry about because we are legally in international waters."

Mr Elwartowski and Ocean Builders said the couple were not involved in the building or construction of the sea home.

Videos posted to YouTube show the couple being involved in erecting a spar in the ocean and towing the platform home out to sea.

A diagram of the inside of the seastead. ( Supplied: Ocean Builders )

Mr Elwartowski told Reason magazine earlier this year that "the team surrounding the project were early adopters of bitcoin", and had spent some $150,000 on the project.

According to the BBC, he reportedly worked as a software engineer for the US military before investing in the cryptocurrency.

The Thai navy was set to dismantle and sink the structure, according to the Bangkok Post, but Ocean Builders said a signal picked up from the platform indicated it still stood.

Ocean Builders wrote in a statement that GPS signals "independently" showed the structure fell outside Thailand's Contiguous Zone (but outside its territorial waters); however, the ABC has been unable to independently verify its precise location.

"Whether it is still there or not does not matter much to me," Mr Elwartowski said in a separate Facebook post.

"I'm more concerned about Nadia being driven from her home country and her family. Her son is worried. I hope they can be reunited some day soon.

"The person(s) who funded the seastead are concerned about losing the seastead but Nadia and I were just tenants."

ABC/AP