Vietnam and Thailand who were battling each other less than a decade ago, today issued a joint communique paying that improved relations between them would contribute to peace, independence and neutrality.

During the 1960s and early 1970s, Thailand committed an army brigade to serve alongside U.S. forces against the Vietnamese Communists. This morning Vietnam's red flag with a gold star flew amid billboards welcoming a delegation of Vietnamese officials, headed by Vice President and Foreign Minister Nquyen Duy Trihn. Bangkok newspapers displayed pictures of Trinh having an audience with King Bhumipol.

The Vietnamese are completing a tour of non-Communist states in Southeast Asia and the joint Vietnamese-Thai communique said that "the preset situation in Southeast Asia has undergone profound changes."

The statement went on to say that the two countries would exchange ambassadors "as soon as possible." They also agreed to develop trade, economic and technical links.

Significant among those links will be evil air service. Third-country airlines, including American carriers, say they expect to be permitted in flying through Vietnamese airspace between Bangkok and Hong Kong. At present all air lines must detour around the Vietnamese coast.

Vo Dong Giang, vice foreign minister and spokesman for the Vietnamese delegation, compared the new amity between Thailand and his country to a delicate blossom that must be nurtured.

At a press conference, Giang rejected charges by Cambodia that Vietnam is "expansionist and annexation list." Giang said his country respected the integrity of others, because Vietnam was guided by the words of Ho Chi Minh: "There is nothing more precious than independence and freedom."

But Giang accused the Cambodians of "many cruel acts" against civilians on the Vietnamese side of their common border. Giang said there might be legitimate differences of interpretation between Vietnam and Cambodia over border demarcation. It was last demarcated on a map prepared by the French colonial administration in 1954, he said. But, Giang said, it was not sensible to readjust the frontier now especially by violence.

The Vietnamese people have learned what war is like through many decades," Giang said, "Vietnam is not so stupid as to follow in the footsteps of colonialists and imperialists."

(Phan Hien, Vietnam's vice foreign minister and considered to be Hanoi's specialist on border problems, is in Peking, a diplomatic source there told Agence France-Presse. The report triggered speculation that some effort may be under way to negotiate Vietnam's dispute with Cambodia. Hanoi has frequently called for talks while Phnom Penh has said it would never negotiate until Vietnamese forces had withdrawn from its territory).

The Vietnamese came here after visiting three other non-Communist countries of the region: Malaysia, Indonesia, and the Philippines. In Malaysia the Vietnamese urged their hosts to close U.S. naval and air bases.

In Bangkok, junior members of the 20-man delegation made some discreet soundings of diplomatic and journalistic opinion, particularly on the relative influence of China and the Soviet Union here. Both powers are represented in the Thai capital.

Meanwhile, Radio Phnom Penh continued to report extensive Vietnamese penetrations of Cambodian territory, especially north of the Parrot's Beak salient. Cambodian broadcasts spoke of punishing resistance to the Vietnamese invaders were skeptical that the Cambodians had mounted an effective counteroffensive.

Vietnamese infantry, tanks, and artillery were holding positions along six highways lacing eastern Cambodia between the border and the Mekong River, Radio Phenom Penh said.