Dominique Courteille was reportedly picked up by a fishing boat in Indonesian waters, after apparently drifting in a dinghy for many hundreds of kilometres - from Lipe Island near Satun.

The 57-year-old Perth woman was the subject of a three-day air and sea search by Thai Marine Police that was called off late on Sunday.

Australian consular official confirmed late yesterday that Courteille was found alive, but had few details.

The yachtswoman is reportedly in a serious condition. One of her crewmen said last night he was told she was unable to speak after floating at sea for many days without food or water.

Courteille, who has been living in Phuket for the past 18 months, went missing late last Wednesday night. Originally from Belgium, she reportedly has a former husband and four children in Perth, Western Australia.

Thai police were giving her two crewmen a tough time in questioning yesterday - suspecting perhaps that they were involved in her disappearance. That was prior to the news of Courteille being found, at about 4.30pm Thai time.

Crewman Manfred "Richie" Neustifter, 24, originally from the Gold Coast but a resident in Phuket for the past two years, said last night he and Swiss colleague Conrad Ohlier, 43, "just hugged each other when we got the news".

"Conrad is crying," he said from the police station in Satun.

"We were really getting grilled. The [Thai] local police have really been giving us a hard time.

"I'd been about to crack.

"I don't know when they picked her up but they said an Indonesian fishing boat found her in Indonesian waters - that means she has floated through the Malacca Strait!

"They said she was not able to speak. So, it appears she could still die or be in a critical condition. I don't know what she survived on."

The three were sailing Courteille's 11-metre fibreglass yacht "Sonnet" back from Langkawi Island in Malaysia - a journey of about 140 nautical miles, or 260 kilometres.

Neustifter said Courteille had disappeared on Wednesday night without talking to him or Conrad.

"We didn't actually see her go, so we couldn't really do anything," he said by phone from Satun. "We thought she'd just taken the dinghy to the boat and we were expected to sleep on the beach that night.

"The next day we knew something was up - we couldn't see the dinghy and thought 'this is not good'. So we started looking up and down the beach for the dinghy."

The pair were hampered in alerting authorities because Ko Lipe "is a really remote place", and only has power for "a few hours a day and the Internet connection didn't work".

They eventually contacted the Thai Marine Police and a major search was organised, with two vessels sent out and a plane used to do an aerial grid search off the coast.

Courteille is understood to have had problems with depression and Marine Police initially suspected she might have taken her own life. She was also known to be a heavy drinker.

"That night was the lowest tide of the year - 0.3 of a metre - and had the strongest currents of the whole year," Neustifter said. "There were also strong winds that night, up to 30 knots. The dinghy could have gone a long way.

"Working with the Marine Police chief was really good. The whole Navy and Marine Police - their search effort has been as good it would be back in Australia."

The disappearance of Courteille is the second major drama for Neustifter in recent years. The young Aussie was in Phuket when the tsunami struck. He was alerted to the huge waves by yachting colleague and fellow Australian Bill O'Leary, who was offshore and felt the waves go under his vessel. Neustifter managed to raise the alarm and get dozens of hotel guests off the beach near the Amanpuri and Trisara resorts.

Jim Pollard

The Nation