President Carter reaffirmed yesterday the U.S. commitment to the security of Thailand, which is seeking to bolster its military strength since the Vietnamese invasion of its eastern neighbor, Cambodia.

"Our nation is intensely interested and deeply committed to the integrity and to the freedom and the security of Thailand -- that your borders stay inviolate," the president said during a welcoming ceremony at the White House for Thai Prime Minister Kriangsak Chomanan.

After the ceremony, White House officials said, the president sought to back up his comments about concern for Thailand's security by telling Kriangsak he will seek authorization from Congress to transfer to Thailand -- free of charge -- $11.3 million worth of U.S. ammunition that has been stored in that country since the Vietnam War.

U.S. officials stressed Carter's comments about security, although Assistant Secretary of State Richard Holbrooke characterized the reassurance to the Thais as "a routine thing" in the relations between the two countries.

Jerrold Schecter, press spokesman for the National Security Council, conceded that the White House is particularly anxious to reaffirm U.S. commitments to allies such as Thailand since the criticism of the decision to cancel the mutual defense treaty with Taiwan and establish diplomatic relations with the People's Republic of China.

During a 75-minute meeting also attended by aides from both countries, Schecter said, the president told Kriangsak of his concern about the Vietnamese invasion of Cambodia, and promised that the United States will "improve the quality of our military presence in Asia."

Schecter said the latter point involves improving the equipment provided American forces in the Western Pacific -- for examply, upgrading the Seventh Fleet.

He said the two leaders also discussed narcotics control, U.S. military supplies to Thailand and the flight of Indochina refugees.

Concern for Thailand's security was underscored last month when the administration increased military aid to Thailand to $30 million for the current fiscal year, up $6 million.

But while that action and Carter's remarks yesterday were aimed at reasserting support for Thailand, Holbrooke stressed that the Thai government has not been directly threatened by the events in Cambodia.

"The general feeling of most people at this point is that the situation is well in hand as far as the Thais are concerned," he said.

In their public remarks during the welcoming ceremony, both Carter and Kriangsak referred to the fighting in Cambodia.

"You come here at a very important time, when our own region of the world is again witnessing conflict at your very shores and borders, a time of mutual concern," the president said.

The United States, he added, is "very deeply interested in the independence and the security of the people of Southeast Asia."

Kriangsak said, "I regret that the peace and stability that we long for in Southeast Asia has not yet been established. The killing still goes on. While the present situation has dangers, we are confident that the strength and the resiliency of the Thai people will enable us to withstand all challenges."

In a reference to his desire for additional U.S. military aid, Kriangsak said that while Thailand will rely on its own people for its defense "we will need your cooperation in improving our military deterrent."

Kriangsak was in Washington at the start of a 12-day official visit to the United States. He is also scheduled to travel to New York, Palm Springs, Calif., Los Angeles and Honolulu.