[2] Thammanoon Thien-ngern was born on 28 June 1913 in Phan Thong district, Chonburi province, Siam and is of Chinese descent.

Thammanoon moved to Phra Nakhon Si Ayutthaya where he was elected as an MP in 1969 for the Democrat party.

He had only served for two years when in November 1971, Prime-minister Thanom Kittikachorn staged a coup against the government, closing the House of Representatives.

[5] The 1975 Bangkok gubernatorial election was held on 10 August 1975 and was contested by five candidates including Thammanoon of the Democrat party.

Conflicts between Thammanoon and the Bangkok Metropolitan Administration led to his removal by Prime-minister Thanin Kraivichien on 29 April 1977.