WHEN the mobile telephone on the bridge of the Mermaid No 1 rang a few kilometres outside Hongkong waters, captain Jeon Jong-jin listened carefully as the ''Mr Big'' gave him instructions. It was to be the first of many such calls the Korean master was to receive during a hazardous six-month journey. It was a journey that ended in a steamy Central American detention camp. Caught in a tangled web of greed, misery and exploitation, Jeon was ordered to steer his ship crammed with 235 Chinese migrants into the South China Sea, across the Indian Ocean to the Cape of Good Hope, and then across the Atlantic Ocean. He was to become a key figure at the centre of a well-organised human smuggling ring - moving hundreds of people across international borders - with access to money, modern communications, international connections. Picked up by the United States Coast Guard in international waters off the Bahamas in April, the Mermaid was eventually escorted to Honduras - for ''humanitarian reasons'' - in May, where the Korean crew and their Chinese ''cargo'' were detained. But Jeon, unlike most Chinese involved in the racket who have remained silent, has given US investigators a remarkable insight into the workings of the human-smuggling ring. His account of the ill-fated voyage, obtained by the Sunday Morning Post, has exposed a new trend and sophistication in the billion-dollar trade under investigation by an inter-agency task force under the top US Government agency, the National Security Council. At the core of his claims are allegations of Chinese ''naval'' involvement and a move away from the traditional loading areas of Fujian province and Taiwan to remote areas in Guangdong. One recent, unconfirmed report even had ''snakeheads'' brazenly loading a ship with US-bound illegal immigrants in Shekou. And in a sign of the business-like approach - and frequency - of these trips, the US Coast Guard discovered a US$500,000 (HK$3.9 million) contract between the owner and the charterer detailing payment and when they would board the vessel. In his interview with US authorities, Jeon said the odyssey began at the South Korean port of Pusan where the Mermaid was hired by a ''charterer''. The 400-tonne merchant vessel left Pusan on January 17 for a rendezvous 30 nautical miles to the west of Hongkong. He told officials he anchored at a group of islands in the mouth of the Pearl River estuary, called Qingzhou Shuidao, on January 29 and was met by ''naval'' speedboats, although he gave no identifying marks or numbers. The captain said 120 Chinese were ferried to the Mermaid in batches of 40 from a base on one of the islands. The ship then sailed through Chinese waters to the south of the territory, skirting Hongkong's marine boundary to the second collection point. At no time did the captain of the Mermaid, which is on a US list of ships involved or suspected of being involved in smuggling illegal immigrants, report his position to Hongkong officials. ''There is an awful lot of shipping going around that is not tracked,'' a Marine Department official said. On February 10, Jeon said the ship developed engine problems as he picked up the remaining illegal immigrants from an unspecified point off Daya Bay, to the east of Hongkong. The Korean said he was again met by naval speedboats although, as he had no further description of the boats. In both rendezvous, and all future movements, the captain was instructed where to go and when to be there by the ''organiser'' on a mobile telephone. The ship then sailed for Singapore where it stayed from February 17 to February 25 while it was restocked with food and water, and where a small motor was replaced. While in Singapore, Jeon said he received his final instructions from the organiser, believed to have flown to the island state to meet the ship. The Mermaid then sailed for eight weeks through the Java Sea and headed for South Africa where it turned northwest for the US. The US Coast Guard first sighted the vessel on April 21 and later boarded the ship after receiving permission from the Honduran Government. The ship was escorted to the Honduran port of La Ceiba, on the east coast of the Central American country, in a move aimed at holding the aliens in a third country and out of the US to stop them claiming political asylum. The Korean captain and his crew were taken into custody on May 11 while the Chinese were held in a temporary detention centre at a Mennonite community centre while negotiations took place to repatriate them. The US authorities were intrigued by ''The Contract of Agreement'' between the ship's owner and the unknown Mr Big, a detailed document written in bad English which laid out the terms of the deal. It stated the charter fee was US$500,000 for one trip for 200 passengers, with the port of embarkation listed as Pusan. The two-page document said the ship was not to set off without a deposit of US$80,000 being paid at least five days before departure. It warned the charterer to stay out of US and Chinese territorial waters, and outlined the responsibilities if somethingwent wrong during the trip. ''In the case our ship is arrested by US Coast Guards and/or Chinese Coast Guards, the charterers are responsible for solving this problem at the charterers expense,'' the contract said. ''A deposit of US$80,000 shall be deposited to the ship's owner five days prior to sailing from Korea and the balance of US$420,000 should be paid before the arrival at Singapore,'' the document said. It then warned the charterer that if he failed to abide by this then ''all rights and actions'' would revert to the ship's owner. According to the contract the owner was responsible for all engine and mechanical problems and those caused by the Korean crew. While the charterer was responsible for problems caused by the immigrants during the trip. This is believed to be the first time a contract has been discovered by authorities and sheds further light on how agreements are reached and the amount of money involved. One estimate by a private lawyer in the US puts the figure at US$3.1 billion for 1991 alone, a period most authorities believe is well below last year in terms of the numbers of arrivals. The involvement of the Mermaid has again focused attention on Hongkong's involvement in the organised crime-controlled trade, with the ''organiser'' suspected of operating out of the territory to set up the trip. In all, the US Coast Guard has detained more than 1,600 illegal Chinese immigrants this year, more than twice the number taken into custody off the US coastline in 1992. The racket seems set to continue. A US official in Honduras said the Chinese immigrants had been charged US$5,000 for the trip, with a US$25,000 drop-off fee due on arrival. Last Monday, under the guidance of the Hongkong wing of the International Organisation for Migration (IOM), 233 Chinese - of 235, one had died and one was injured during an escape attempt in Honduras - were repatriated. Escorted by 60 Hongkong security guards, the Chinese were flown to Xiamen via Bermuda and Bombay, according to Honduran immigration chief Mario Boquin. The guards were provided by Securair Limited and Far East Air Charters. A Securair spokesman said the guards flew to Honduras after being contacted by the IOM, adding there was ''no problem'' with the trip. IOM Chief of Mission in Hongkong Alfred Kottek, who organised the flight, said: ''They were returning voluntarily, they were not being deported. ''This is a migration issue. If there are people in need of assistance then we would intervene so that they can return in dignity.'' Dr Kottek said he hired Hongkong guards because they spoke the same language. There had been a communication problem with the Hondurans. The immigrants' stay at a makeshift Honduran detention centre from May 11 had cost the US Government US$2 million.