An American man and his Thai wife, accused of illegally building a so-called seastead close to Thai territorial waters in the Andaman Sea, are believed to be hiding on Tarutao Island to escape police arrest.
A seastead is a permanent settlement on a structure located at sea outside the jurisdiction of any country.
Officers in Phuket are forming a team to hunt the couple after seizing their house, viewed as a threat to Thai sovereignty and the environment, and taking it ashore late on Monday night.
"We're waiting for the attorney-general to assign co-investigators to join the team and will soon seek an arrest warrant," Phuket police chief Wisan Panmanee said yesterday.
Both parties -- Chad Andrew Elwartowski and his wife Supranee "Nadia" Thepdet -- are likely to face more than one count of wrongdoing, not just their alleged violation of Section 119 of the Criminal Code, which prohibits any act that undermines the sovereignty of Thailand, Pol Maj Gen Wisan said.
The 46-year-old American bitcoin investor and Ms Supranee were not in their seastead during an inspection on April 12. The latest clue indicated both were in Tarutao, Pol Maj Gen Wisan said, but believed they already turned off their smartphones to prevent investigators locating their whereabouts.
"I can't tell more details. What I can say is we believe they've not left the country," he said.
The investigators earlier found the couple had allegedly persuaded people to build seasteads off the coast of Phuket. They claimed the area is in international waters, so it can be declared a so-called independent state.
The couple's floating house -- a six metre-wide platform installed by Ocean Builders -- was located about 14 nautical miles (26 kilometres) off the Phuket shoreline.
Thai authorities insist it was in the country's contiguous zone over which it has jurisdiction and rights.
Third Naval Area chief Sittiporn Maskasem said the seastead was poorly built and flouted guidelines to prevent collisions at sea.