Prime Minister Prayut Chan-o-cha expressed support for Washington's "constructive role" in the region during his conversation with US President Donald Trump, a deputy government spokesman said on Monday.
The US president called Gen Prayut in Bangkok on Sunday night.
Thailand was ready "to support the constructive role of the US in maintaining peace and security in the region", Lt Gen Werachon Sukondhapatipak said.
Gen Prayut pledged closer cooperation with the US in all areas, from trade to investment and security, the deputy spokesman added.
He also thanked Mr Trump for his condolence message on the passing of King Bhumibol Adulyadej.
The US president made phone calls to the leaders of three Southeast Asian leaders overnight - Thailand, Singapore and the Philippines - amid rising tensions on the Korean Peninsula.
"President Trump affirmed the commitment of the United States to playing an active and leading role in Asia, in close cooperation with partners and allies like Thailand," the White House announcement said.
Gen Prayut and the president spoke ahead of a meeting in Washington on Thursday, when US Secretary of State Rex Tillerson hosts the foreign ministers of the Association of Southeast Asian Nations (Asean).
The US and Asean ministers are expected to focus on North Korea's aggressive development of nuclear weapons and ballistic missiles, and China's assertive territorial claims in the South China Sea, as well as US trade policy towards Asia following Washington's withdrawal from the Trans-Pacific Partnership trade pact.
US President Donald Trump speaks with the Thai, Singapore leaders on North Korea nuclear threat. (Reuters video)