Vietnam, embroiled in a war with Cambodia, has begun drafting more young men from its southern cities and is increasing efforts to stop illegal emigration, according to South Vietnamese refugees arriving here.

Several former university students and one former soldier of the defunct South Vietnamese government said they hid when draft officials came to their homes in Qanang earlier this month. Along with wives, sisters and children they left the city by fishing boat and arrived here Monday.

The refugees provided the most recent account of the Vietnamese-Cambodian war's impact on life in southern Vietnam, thousands of whose residents have been fleeing to escape the harsh new regulations imposed by the Communist officials from the north. Their account appears to back up the latest official reports from Vietnam indicating that the Hanoi government considers the fighting to be quite serious.

"They're taking anyone who is 13 and in some areas friends have told me they are taking 14- to 16-year-old boys," said a former student. He said he became subject to the draft when the Communists expelled him from his university because he was a Roman Catholic.

"After they had announced the break in relations (with Cambodia) and the heavy fighting, we heard they were increasing the patrols offshore," said the former soldier. He said he had traveled illegally between Saigon and Danang several times to arrange bribes and equipment for the fishing boat escape. The refugees declined to say how they had eluded the patrols or to give their names for fear of harming other potential refugees or relatives still in Vietnam.

Western observers said they detected a lull in hostilities over the past week, but the Vietnamese news agency reported today a multi-battalion engagement with Cambodian troops as late as Tuesday.

A senior Chinese delegation led by the late Premier Chou En-lai's wife, Teng Ying-chao, was dispatched to Cambodia yesterday apparently to confer on the war with officials in Phnom Penh. The Cambodian radio account of Teng's remarks at a reception last night gave little hint as to whether she was advising the Cambodians to make peace or keep fighting.

Teng assured the Cambodians they had the support of China and the people of the world." She urged all socialist countries to observe the principles of peaceful coexistence "in the struggle for independence sovereignty and territorial integrity."

Since Cambodia and Vietnam broke off relations Dec. 31 and escalated their long-time border dispute, Peking has declined to lean very heavily toward the side of its ally, Cambodia. The official Chinese News agency has published some of the official Vietnamese statements on the conflict despite the distrust Peking feels toward Hanoi and the hatred it bears for Hanoi's ally, the Soviet Union. The Chinese appear to hope the Cambodians can prevent any Vietnamese advances while keeping the fighting at a low level that does not force Hanoi to call for more Soviet weaponry.

The refugees, arriving here exemplified Vietnam's morale problem. The draftees who fought on Hanoi's side in the civil war that ended in victory in 1975, were influenced by the 20-year-old dream of reunited country that had some popularity in the North. Many of the draftees for the war against Cambodia are southern youths weary of the civil war and resentful of the break-up of their families and loss of privileges forced by their conquerors from the north.

If the war with Cambodia would weaken the Communist government in Vietnam then I'm for the Cambodians, said a refugee reaching here. The refugees said draftees were given minimal training before being sent to the front where Western analysts estimate that $50,000 to 60,000 Vietnamese soldiers face about 20,000 to 25,000 Cambodians.

Hanoi called Monday for "combining economic development and the consolidation of national defense" to win the war, which to the refugees means continued low food rations. They said they were able to get only about one-fifth as much rice as was available before 1975 and had to fill out their diet with corn and wheat meal. They said there was almost no meat.

Foreign observers have speculated that the Chinese might be trying to mediate the conflict because of the sudden mission to Cambodia a week after the arrival in Peking of Vietnamese Deputy Foreign Minister Phan Hien.

But the Cambodians have not stopped making belligerent public statements. In response, Hanoi accused them today of a string of border offenses between Jan 9, and 17, including a Jan. 11 assault in which 23 Vietnamese civilians died and 213 houses and tons of rice were burned.