Lush drama set in Laos -- plus black unions in S. Africa

Love Is Forever (Sunday, NBC, 8-11 p.m.)m is a lush, romantic drama about the love between an American magazine writer and a Laotian dancer and medical student who manage to overcome such obstacles as politics and environment.

The film stars Michael Landon, the ''Little House on the Prairie'' man-of-all-talents (actor, producer, director, writer, sometime cinematographer and who knows what else), and co-stars Indonesian actress Moira Chen.

''Love Is Forever'' is not a perfect work, however. This film is a kind of small-screen minor-league combination of ''Love Is a Many Splendored Thing'' and ''Bridge Over the River Kwai'' (although it is in foreign distribution as a theatrical film). It's just a bit too slick, a bit too schmaltzy, and much too long. But despite those shortcomings, it is the kind of old-fashioned love story seldom seen on TV - or, perhaps even in life - these days. Two people fall in love and overcome enormous problems to consummate that love legally, in a democracy, idyllically.

Based upon the much-publicized true story of John Everingham, who was expelled from Laos after reporting on the terror of the Pathet Lao dictatorship, ''Love Is Forever'' is a film with a conscience. It doesn't neglect the plight of the Laotian and Cambodian ''boat people'' fleeing communist persecution, as it tracks the love story of a Laotian lucky enough to have a protector willing to risk a breathtaking rescue jaunt underwater across the Mekong River. Of course, more could have been included about the boat people - but this is basically a love story, as the constant repetition of the syrupy theme song constantly reminds viewers.

''Love Is Forever'' will have viewers rooting for the gentle lovers against the story's depiction of communist attempts to manipulate men's minds. Alternating love and action scenes, throwing in an extraordinary East-West boxing match and the long underwater journey, superimposing some mushy music and slightly phony factual data, ''Love Is Forever'' emerges as an unexpected pleasure. Blacks in South Africa

Will South African blacks win their human rights through their labor unions?

That's a question posed and answered with a resounding ''Probably'' in the ABC News Closeup Adapt or Die (ABC, Friday, 10-11 p.m.)m - a bold examination of the emerging black trade union movement in South African gold mining and auto manufacturing industries. It is a documentary about change, about inevitable change, and the unique way it seems to be coming about in South Africa.

''Adapt or Die,'' produced by Christopher Isham, and directed by Pat Cook, is a powerful, frightening, yet somehow uplifting documentary. Its airing in this country will help clarify for American audiences the complexity of the ongoing struggle in South Africa and the determination among some blacks that they will find their own way to overcome. If only it could be aired in South Africa as well. . . .

According to writer-correspondent Marshall Frady: ''South Africa suppresses 80 percent of its people . . . black South Africans. They have been virtually erased as citizens of this land . . . . That suppression has produced a tide of violence. . . . The prime minister finally warned white South Africa it must 'adapt or die.' And after a siege of black labor unrest, the government in 1979 legalized black trade unions . . . . But now many black unions have met with grim government reprisals . . . [yet] in four years, membership has soared to close to 500,000 workers.''

According to one black labor leader, Ntatho Motlana, ''This process is completely unstoppable. And it is the one great ray of hope in the future that, indeed, things may change without violence.''

The documentary, in a series of interviews and investigations, looks in on union leaders, union workers, ordinary South African blacks, and white government leaders. Appearing on camera constituted an act of extreme bravery on the part of most black leaders. But they did it because they hoped that the film would reflect the idea that there can be civil-rights liberation for blacks without the bloody conflict so many activists are predicting.

Even though white South African officials show few signs of allowing the black unions to assume the enormous power over the economy they could one day wield, Mr. Frady comes to the conclusion that ''what has begun here has given South Africa's blacks a feeling, for the first time, of their own power . . . and for them there will never be any going back.''Mr. Isham wants to make it clear he believes the documentary is not merely a finger-pointing criticism. He feels it is a positive and constructive contribution to ''a story about a dramatic change coming from the people, building on its own momentum.''

Might it be shown in South Africa? ''I'd love it to be shown there,'' he says , ''but remember that all TV in South Africa is controlled by the government. The white government. So . . . .'' Of Blythe and Mariette

Two of my favorite actresses - Blythe Danner and Mariette Hartley - are sparkling their way to TV screens during the next few days.

Blythe Danner stars with Sam Waterston in what may be a controversial little drama about children's rights: In Defense of Kids m(CBS, Wednesday, 9-11 p.m.)m. While abused children obviously need legal representation, there could be some disagreement as to where the protection of kids becomes interference in family life by outside lawyers and courts. I must confess I felt some degree of release when at one point Miss Danner, in the role of a lawyer who devotes her life to protecting the rights of children, blows up at one of her impossible young charges and accuses her of being a ''selfish brat.''

But the drama confronts the issues honestly and viewers may find preconceived attitudes changing under the beguiling influence of this persuasive, pervasively charming actress.

Miss Hartley is another talented charmer, who last week proved to be outstanding in the NBC drama about drunken drivers. She played the mother of a daughter killed by a drunk driver who devotes her life to a crusade against alcohol. Now Miss Hartley is starring in a limited series which CBS obviously hopes will prove to be successful enough to find a place in the regular schedule: Good Night, Beantown (CBS, Sundays, 8-8:30 p.m.)m. Certainly, CBS has given it a prime spot - directly after ''60 Minutes.''

I have previewed the first episode of this series about a pair of Boston TV anchor people and found it to be a harmlessly charming, vaguely amusing show that delves deeper than might appear on the surface.

Miss Hartley, whom you may know best from her Polaroid commercials as James Garner's wife, is an engaging actress, whose personal strength somehow invades any fictional character she plays. The premiere segment of the series allows her to be strong, determined, aggressive. Don't expect her to play the role of a submissive little starlet.

Indirectly the series deals with such things as happy-talk news, co-anchor rivalry, the women's movement, sexism. But most subliminally. On the surface it is just a pleasant way to while away half an hour on a Sunday evening . . . with the company of Mariette and company.