Andreas du Plessis de Richelieu

At 23 years old in 1875 he was granted an audience in Copenhagen by the Danish king Christian IX where he wished for a Letter of Introduction to the King of Siam, Chulalongkorn. Andreas would then sail from Denmark to Bangkok via Singapore and with assistance from the Danish consul, he was given an audience by Chulalongkorn on 3 April 1875. The fact that Andreas was not significantly taller than the King was important in Siamese society and both Andreas and Chulalongkorn would form a friendship between the two. A couple weeks after his meating with Chulalongkorn, he became Captain-Lieutenant and was offered the role of second-in-command of one of the navy's ships which he turned down for command of his own ship, HSMS Regent.[6]

Chulalongkorn in Norway. Chulalongkorn is in the center sitting with Andreas behind him

In 1878, he was appointed Captain of the Royal Yacht Vesatri. In 1878 he became superintendent of the Marine Forces. However to Siam's navy being small, Andreas occupied himself with other projects such as establishing railways and tramlines in Bangkok. He also learnt Thai. In 1884 he established Andersen & Co. (later the EAC) with Danish business partner Hans Niels Anderson and their company owned the Oriental Hotel in Bangkok, which became the first Western hotel in Thailand. They also established the Oriental Provision Store which became the main supplier of goods to the Marine forces and the Vesatri due to Andreas' role as superintendent. In 1892, they would delivered a new royal yacht called the Maha Chakri which Hans Anderson sailed from Scotland to Siam.[4]

In 1891, he was chosen by Chulalongkorn as an envoy on a private diplomatic mission to France, Denmark and the Russian Empire along with the king's brother Prince Damrong Rajanubhab. As Chulalongkorn continued to modernize his country, the EAC paid for concessions in industries such as teak tree logging. Andreas also acquired concessions such as building and operating a 21-kilometer railway from Samut Prakan to Bangkok.

Hans Niels Andersen and Andreas du Plessis du Richelieu in 1932

Though the project would run out of funds, Chulalongkorn would become a shareholder and invest ฿170,000. The railway was inaugurated in July 1891 and would operate until 1959 where it became a tramline.[4] He would also lead the construction of the first electric tramline in the country which ran 18 km from the Royal Palace to Klong Toey, with Fleuron Jacobsen becoming the project's manager. It opened in 1894 under Danish ownership by Chulalongkorn.

The most important concession given to Andreas was the Siam Electric Company Ltd. which he obtained in 1898. Siam Electric had the sole responsibility of delivering electricity to Bangkok and its 40,000 inhabitants. The concession was originally an extendable 10-year concession granted for American L. E. Bennet but was sold to Andreas.[7] The company would prove profitable along with the electric tramline it powered, generating 1,200,000 Danish Crowns. In 1912 the majority of stocks were sold to Belgians.[4]

Andreas' sarcophagus at Church of Holmen, Copenhagen, Denmark

Andreas left Siam in 1902 on board the Royal yacht Maha Chakri for Singapore while accompanied by Chulalongkorn and other royal family members. Once in Denmark, be rented then purchased Kokkedal Castle in North Zealand. He also operated a private railway line from Copenhagen to Slangerup. In 1922, one of his companies - Landmandsbanken - collapsed and in 1923 he was fined 4,000 Danish Crowns after being convicted of gross negligence by the Danish Supreme Court. Despite being in Denmark, he maintained close relationships with Chulalongkorn and Prince Damrong who both visited him in Denmark, with Prince Damrong making the last visit to Andreas in 1930. He died age 80 on 25 March 1932 in Hørsholm, Denmark.[4]

His family was present in Denmark from since the 1000s.[9] His Danish ancestors had married ancestors from Norway who migrated there from Schleswig-Holstein.[10] Many of his Danish ancestors on his paternal side originated from Svendborg.[11] On his paternal side, some of his ancestors were buried in Rome.[12] His paternal side also has traces to Klinte, Sweden;[13] German nobility; Bohemian royalty;[14] Obodrite royalty;[15] Moravian royalty;[16] Herulii royalty;[17] Gothic;[18] Sorbian;[19] Polish royalty;[20] Ukrainian royalty;[21] and Kievan Rus;[22] English nobility;[23] English crusaders;[24] Norman nobilty;[25] Scottish nobilty[26] Notable ancestors on his paternal side include Wiprecht of Groitzsch, Vratislaus II of Bohemia, Bořivoj, Radagaisus, Casimir I, Saint Olga of Kiev, and Edward III of England.

Andrea's wife Dagmar on the right in Thailand besides Chum Krairiksh and Saovabha Phongsri

Together with Dagmar, he would father 3 sons and 3 daughters. Their first child and son Louis Armand was born in Bangkok on 16 November 1892 and lived 82 years until his death on 16 November 1974.[27] Helge was born as their second son on 14 February 1894 and lived to 21 April 1975 at 81 years old.[28] Dagmar was born in Bangkok on 8 May 1895 and lived 85 years to 8 February 1981.[29] Agnes Ingeborg was their second daughter and was born on 25 February 1897 before dying on an unknown date.[30] Lilian Agnete was their first child born in Denmark on 2 February 1903 until her death.[31] Their final child was Louis.[32] In total Andreas had 6 children, 6 grandchildren, 14 great-grandchildren, 3 great-great-children.