Viet attack a taunt at Reagan?

Vietnamese troops have thrust across the Thai border for the second time in six months. Observers suggest that the Vietnamese, who rarely act for military reasons alone, may have timed their attack to show they are not intimidated by the "hawkish" rhetoric of incoming President Reagan.

The action also appears to be an effort to scuttle an upcoming three-day UN conference in Manila on the Cambodian crisis. China and the Association of Southeast Asian Nations (ASEAN) are among those supporting the conference. Vietnam, the Soviet Union, and the Vietnamese-dominated Cambodian government of Heng Samrin are opposed.

Saturday's attack by Vietnamese soldiers carrying automatic weapons and rocket- propelled grenades, was presumably aimed primarily at the anti-Vietnamese guerrilla groups that quietly slip out of Cambodia and into Thailand for sanctuary. Two Thais were killed and one wounded in the 90-minute clash. No Vietnamese casualties were reported.

Thai policymakers presumably hope the attack will impress the Reagan administration with the need to buttress Thailand firmly against Vietnamese aggression.