Vietnam has taken the first step in establishing a Cambodian rebel movement to challenge the political authority of the Phnom Penh government, according to analysts here.

In a Hanoi Radio broadcast a Cambodain defector has proclaimed the existence of "revolutionary forces" in side Cambodia "who have already . . . established a base to fight against" the Phnom Penh regime.

The move was reminiscent of Hanoi's initial steps in its campaign against the U.S. supported government of South Vietnam in the late 1950s. Eventually the Communist leaders of North Vietnam created a National Liberation Front composed of South Vietnamese. Ostensibly the Front directed the was against the Saigon government but the real control was excercised by Hanoi.

Creation of a rebel Cambodian movement would indicate Hanoi has virtually abandoned hope of reaching a negotiated settlement of its violent dipsute with the Phnom Penh. Hanoi has insisted the quarrel stems from territorial disputes but Phnom Penh says the real issue is an attempt by Vietnam to dominate it.

The Cambodian defector was identified as Run Dun whose statement said and member of the Cambodian Comhe was a former battalion commander munist Party. Run Dun, said he and several other officers were arrested in May during one of the periodic purges that have swept through the middle echelons of the Cambodian hierarchy. Taken in trucks with other officers to an execution site, he escaped under machinegun fire and made his way to Vietnam, he said in the statement broadcast June 22.

Run Dun said the "revolutionary forces" were centered in Cambodian Military Zone 203, which intelligence sources here believe is around the town of Mimot in eastern Cambodia.

Mimot is about six miles north of the Vietnamese border and reportedly was the scene of some fighting in the offensive mounted by Hanoi in the later part of June.

There is speculation here that the recent thrust by the Vietnamese in the Mimot area may have been for purposes or supplying and reinforcing the "revolutionary forces" said to be there.

Travelers in Vietnam have reportedly indications that the Vietnamese have begun training Cambodian youths for what is presumed to be a rebel force against Phnom Penh. They would have a pool of 100,000 refugees from the Cambodian Communist government that came to power in April 1975 plus some 1 million ethnic Cambodians living in the Mekong Delta area of southern Vietnam.

A June 25 broadcast by Phnom Penh Radio indicated the Cambodians have been expecting the Vietnamese to establish some revolutionary challenge to their authority. The Cambodian statement said:

"Should (Vietnam) fail in conquering the whole of Cambodia, it will separate the eastern part of Cambodia and form a new administration for that region. It will make use of this eastern region as a stepping-stone to attack and seize the area of Cambodia east of the Mekong River by military force, and other parts of Cambodia afterward."

The official told foreign correspondents visiting the area that the Vietnamese were building up their troop strength along the frontier, building roads and adding security check points.

Relations between Hanoi and Peking have deteriorated sharply in recent months with the mass exodus of Chinese from Vietnam.

Pan Ching-sen, deputy director of the Yunnan provincial office dealing with foreigners, said the shooting incident occured Tuesday when the two Chinese workers were swimming in the Red River, which marks the border.

The were not hurt but were held several hours by the Vietnamese for questioning, he said.

[The Soviet Communist Party newspaper Pravada yesterday accused China of carrying out "new provocative actions" against Vietnam on behalf of Cambodia. It said China was using the issue of "supposedly persecuted" Chinese nationals in Vietnam as a pretext for "trying high-handedly to interfere in Vietnam's internal affairs."]