His father, Phraya Phiphaksa Satayathipatai (Po Khoman) was one of Siam's first law school graduates and a judge on the Supreme Court of Thailand.

[6][7] After his return to Thailand, Thanat was obliged to join the diplomatic service, as the foreign ministry had financed his studies.

In February 1945, he was a member of a secret delegation to the Allied South East Asia Command in Kandy, Ceylon.

[8][9] After the Second World War, he held a number of diplomatic posts, including chargé d'affaires at the Thai embassies in Washington, D.C., and Delhi.

The choice of Bangkok as the founding place of the Association of Southeast Asian Nations on 8 August 1967 was an expression of respect for his active role in the formation of this institution.

After his resignation as foreign minister, Thanat entered national politics in 1979 and served as chairman of the Democrat Party until 1982.