Authorities have raided a floating home in the Andaman Sea belonging to an American man and his Thai partner who sought to be pioneers in the "seasteading" movement, which promotes living in international waters to be free of any nation's laws.
The Royal Thai Navy said they endangered national sovereignty, an offence punishable by life imprisonment or death.
The navy filed a complaint against them with police on the southern resort island of Phuket.
Chad Elwartowski said in an email Thursday that he believes he and Supranee Thepdet did nothing wrong.
The couple, who have gone into hiding, had been living part-time on a small structure they said was anchored outside Thailand's territorial waters, just over 12 nautical miles from shore. Thai authorities say they have revoked Mr Elwartowski's visa.