The couple claim the home is outside Thai waters.

(CNN) An American bitcoin trader and his girlfriend could face the death penalty after they were accused of threatening Thailand's sovereignty by building and living in a "sea home" off the coast of Phuket.

Chad Elwartowski and his partner Nadia Supranee Thepdet have fled their home, built atop a platform around 12 miles off the coast of Phuket, and gone into hiding after authorities revoked the American's visa.

He had promoted "seasteads" on social media and claimed his home did not fall under the sovereignty of any country, which Thai authorities have said is untrue. He repeated the claim on Thursday, writing the home is "outside of Thailand territorial waters."

The couple could face life imprisonment or the death penalty under the country's Immigration Act, but authorities told CNN they are unaware if the pair are still in the country or its waters.

"Nadia and I are still safe," Elwartowski wrote on Facebook on Tuesday, adding he was unsure whether their home had been destroyed. "Whether it is still there or not does not matter much to me. 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."

"It was my home," Elwartowski added. In an earlier post, he said the pair did not design or construct the home but worked with the company that did.

"As long as Nadia and I are able to live through this that is all that matters to us right now. We just want to live," he wrote.

Thailand's navy has said the pair are threatening the country's sovereignty. "By claiming they own a floating house and using social media tried to sell this kind of house, also they claimed that their house is not under any country's sovereignty, which is not true. And this could cause other people to misunderstand and it is threatening our national security," said Colonel Kataporn Kumthieng, the chief of Phuket's Immigration office.

He described the case as "urgent."

The Thai Navy had previously posted a video of the home on Facebook, writing that "the navy is required to resolve the problem."

Elwartowski had taken part in videos and podcasts promoting the use of "seasteads," frequently mentioning how he was unaffected by policy decisions and taxation laws set by governments.

The "seasteading" movement, which began in earnest in 2008 in California with the financial backing of Silicon Valley billionaire Peter Thiel, has been likened to the phenomenon of micronations for its vision of establishing sovereign communities outside the control of existing states.

Ocean Builders, the company behind Elwartowski's seastead, said in a statement on its website that it had constructed the home, the first in what it hoped would be an opening round of 20 units. The couple were "volunteers excited about the prospect of living free", it added.

Insisting the six-meter platform was 13 nautical miles from Thailand and in international waters, the company accused the Thai authorities of acting as "judge jury and executioner of the historic very first seastead." It hoped to resolve the issue "diplomatically," it said.

The Seasteading Institute, the organization backed by Thiel, is currently in negotiations with the government of French Polynesia to build a floating city in a semi-autonomous "seazone" within its territorial waters.