PRESIDENT MARCOS of the Philippines, unwelcome in Washington for the last 16 years, returns now as something of a lion. He is defiantly anti-communist, his country provides important air and naval bases to the United States, and he runs an economy hospitable to free enterprise. Only last year Vice President Bush hailed his "adherence to democratic principles." Everything seems just fine.

But everything isn't fine. Mr. Marcos is a strongman who, while not lacking a political hand, relies on a military one. By his personal rule he has aggravated the substantial "natural" difficulties of a developing country and nourished conditions in which the existing misery, inequality and corruption could explode. That would bring great additional suffering and uncertainty to the Philippines, and give the United States reason to rue its decision to put strategic things first in Manila.

Mr. Marcos was smart. He sensed after the American debacle in Indochina that the United States would feel a need to assert a military presence off the rim of Asia. Thus did the Ford and (yes) Carter administrations write a new bases agreement and bite their tongues on the dismal Marcos record on human rights. Mr. Reagan, feeling that human rights should not become a matter of public disputation with friendly countries, took over from there. He dispatched his vice president to give a completely unjustified blessing to Mr. Marcos. His first secretary of state propelled to signature a new extradition treaty that would let President Marcos snatch back his exiled political foes--or so they believe.

Mr. Marcos is said to be coming to Washington chiefly for the show of affinity with Mr. Reagan. There is no point in expecting Mr. Reagan to spite his own policy and to read his guest a civics lesson in the Rose Garden. Is it not possible, however, for Mr. Reagan to take Mr. Marcos aside for a friendly chat on the need and value, for the Philippines, of moving back toward the Philippines' own democratic traditions? Few people doubt that the country faces real problems of terror, subversion and secession, some of it with a communist taint. What people of good will suspect is that Mr. Marcos, by his arbitrariness, is making the situation worse. No one is better placed to convey this message than Ronald Reagan.