When Siam opened to foreign trade after the signing of the Bowring Treaty, the sailors that crewed the ships though Bangkok required accommodation on shore.

Andersen identified a need for a respectable hotel with good accommodation, a bar, and a western menu to meet the needs of travelers and businessmen visiting Siam.

[4] To ensure the success of the restaurant and a satisfactory level of service, the owners lured the chef and butler from the French Consulate away to work at the hotel.

She sold the property in 1932, but during World War Two, it was leased by the Japanese Army and used as an officer's club (under management by the Imperial Hotel of Tokyo).

The partnership consisted of Germaine Krull (1897–1985), Prince Bhanu, General Chai Prateepasen, Pote Sarasin (prominent businessman and lawyer) and John Webster and Jim Thompson, two Americans who had served in the Office of Strategic Services (OSS) and who had stayed on in Thailand.

[2] In 1967, fearful that Thailand would fall to the communists, Krull sold her share to Italthai which at the time was well on its way to becoming one of the country’s most significant mercantile groups eventually totaling some 60 companies involved in almost all aspects of the Thai economy.

[2] The Group began with the opening of its flagship property, The Mandarin, in Hong Kong in 1963, which soon built up a reputation for luxurious service.

The two-story Authors' Wing, the only remaining structure of the original 19th-century hotel, houses suites named after Joseph Conrad, Somerset Maugham, Noël Coward and James Michener.

The River Wing contains deluxe two-bedroom suites named after former guests or personages associated with the hotel, including Barbara Cartland, Gore Vidal, Graham Greene, Wilbur Smith, John le Carré, Jim Thompson, Norman Mailer, Thai author Kukrit Pramoj.

[10] Other suites are named after ships associated with the early Bangkok trade, such as Otago (once captained by Joseph Conrad), HMS Melita, Vesatri and Natuna.