FOR 30 YEARS almost everybody forgot Tibet. Its exiled spiritual leader, the Dalai Lama, had left the realm of hard news in the West and become merely a quaint feature story. So confident were the Chinese that they had ended all stirrings of rebellion and unrest that they began bringing thousands of tourists into this once-forbidden land. This openness explains how the world knew so quickly of the recent independence demonstrations in Lhasa -- and of their abrupt suppression. Suddenly, Tibet is back on the list of international ''unfinished business.''

It deserves to be there. Conflicting Chinese and Tibetan views on its claim to independence were rudely terminated by the Chinese army, which invaded in 1950 in the name of ''liberation'' and later ruthlessly crushed local resistance -- the ''rape of Tibet.'' Subsequently, Beijing pursued a policy of enforced assimilation, bringing in (and favoring) Chinese settlers, applying police and administrative powers and justifying it all as essential for modernization. The Dalai Lama, who fled to India in 1959, kept the spark of independence glowing, but few beyond the community of believers suspected the spark could again ignite fire.

Recently the Dalai Lama embarked on a new phase of political activism, which included a trip to the United States to publicize a ''peace plan'' aimed at Tibetan independence. His example and word evidently contributed to kindling the demonstrations by (unarmed) Buddhist monks in Lhasa. China protested that the American government had not silenced his political utterances. Of course no American government should do that, but the Reagan administration seems to have let a business-as-usual attitude toward Beijing mute its natural sympathy for local people peacefully opposing totalitarian rule. Congress has not shown a fine diplomatic touch, but it has spoken out vigorously for Tibetan human rights.

The United States cannot go around the world instructing sovereign states to grant independence to restive ethnic minorities, but it should always have available a voice in which to speak for dignity. The monks of Tibet have reminded everyone that China imposed its will by force on a protesting people.