The first documented contacts between Switzerland and Thailand date back to the 17th century. After touring the Kingdom of Siam, Swiss missionaries published accounts of their travels. In the 19th century, Swiss textile companies looked for new business opportunities in South-East Asia.
As early as 1895, the Kingdom of Siam acceded to the Universal Postal Union in Bern and the first Geneva Convention. A Swiss-Thai treaty of friendship and trade signed in 1931 marked the beginning of official relations between the two countries. Switzerland opened a consulate in Bangkok in 1932 and accredited its embassy in New Delhi to Thailand in 1949. In 1959, the Swiss consulate in Bangkok was upgraded to an embassy.
Switzerland and Thailand celebrated 90 years of diplomatic relations in 2021.
Thailand, Historical Dictionary of Switzerland (de, fr, it)
Diplomatic Documents of Switzerland, Dodis