Prime Minister Kriangsak Chomanan ended his two-day visit to Washington yesterday with a pledge from President Carter that the United States will speed delivery of military equipment to Thailand and take "definite action" to defend Thailand from outside aggression.

"The United States has reassured us and given us confidence that if the situation around us escalates, the United States will not stand idly by," Kriangsak told reporters. "The United States will take definite action."

The U.S. commitment to Thailand's security was the major theme of Kriangsak's visit to Washington and was stressed in public remarks by the president. American officials have been anxious to underscore that commitment since the Vietnamese invasion of Thailand's eastern neighbor, Cambodia...

In a joint statement issued yesterday, Carter said the United States "will expedite items of military equipment already ordered by Thailand."

In addition, the administration recently increased the amount of military equipment it will sell to Thailand during the current fiscal year from $24 million to $30 million. The president also told Kriangsak that he will ask Congress to authorize the transfer to Thailand -- free of cost -- of $11.3 million worth of U.S. ammunition that has been stored in that country since the end of the Vietnam war.

The joint statement said that Kriangsak "welcomed" the U.S. decision to establish diplomatic relations with the People's Republic of China, and that both leaders "agreed on the importance of an independent Cambodia to regional stability."

According to the statement, Carter praised Thailand's emphasis on rural development and steps it has taken to curb narcotics production and trafficking. The statement said the two leaders discussed the plight of Indochinese refugees, with the president outlining "his commitment to a long range, systematic U.S. program of resettlement" of the refugees.

Kriangsak told reporters he was "highly satisfied" with his visit. He described as "speculation," but did not deny outright, reports that the Thai government is allowing China to use its ports to supply Cambodian forces still fighting the Vietnamese.