Henry Alabaster was a British national who first arrived in Siam in 1856 during the reign of King Rama IV. He came as a student interpreter to learn Thai before beginning his diplomatic career. He later served as the British Vice-Consul in Bangkok and acted as consul for a time. However, conflicts with another consul led him to resign and return to England.

In 1873, after King Chulalongkorn (Rama V) visited Malaya, Java, and India, he invited Alabaster back to Siam to serve as a personal adviser. Alabaster held several key positions, including Chief Interpreter, Private Secretary to the King, Director of the Museum and Saranrom Garden, and Overseer of road and bridge construction.

One of his most notable achievements was redesigning Saranrom Garden within the Saranrom Palace grounds as a Western-style botanical garden. He introduced many plants, flowers, and orchids — including cattleyas — to the garden.

Alabaster also contributed to the development of surveying and mapping in Siam, which was vital for building roads and planning telegraph lines to places such as Battambang. In 1875, he helped establish the first Surveying Division, serving as its head with both British and Thai assistants. In 1878, he recommended hiring James F. McCarthy from the Indian Survey Department to assist with mapping work, which later evolved into the Royal Thai Survey Department in 1885. Some key milestones in his work include:

  • 1861: Designed and surveyed Charoen Krung Road, the first Western-style road in Siam.
  • 1874: Designed and constructed Saranrom Garden and introduced cattleyas to Siam.
  • 1874: Introduced the lottery to raise funds for the museum.
  • 1875: Established the Surveying Division and began mapping Bangkok.
  • 1881: Recommended McCarthy to assist with mapping.
  • 1883: Contributed to establishing the Postal and Telegraph Departments.

Alabaster died at the age of just 48, after 10 years of loyal service in the Siamese royal court. Because of his dedication and valuable contributions to the country, King Chulalongkorn ensured his family was supported financially and held an honourable funeral for him. His grave at the Protestant Cemetery on Charoen Krung Road features a Western-style monument with his statue.