By Deutsche Presse-Agentur
The nomination of Glyn Davies comes amid a period of tension between the US and Thailand, a country the State Department described as "its oldest ally" in Asia.
Washington suspended military aid to Thailand since the elected government was overthrown by a coup in May. The post of ambassador has been vacant since Kristie Kenney's tenure ended in November.
In response, Thailand has made overtures to China and Russia on military cooperation.
The junta has also summoned the US embassy's charge d'affaires several times over what it perceives as US meddling in the internal affairs of the country.
Davies' nomination still has to be confirmed by the US Senate. He was the Obama administration's lead man in North Korean negotiations.