Parked in the middle of Eritrea's semi-desert, 93 Ethiopian prisoners of war know they're lucky to be alive, but wonder if it's worthwhile.

They know that neither side has taken many prisoners in Eritrea's 16-year-old war for independence.

Their depression does not stem from any mistreatment at the hands of their captors - the Eritrean Liberation Front - who are holding them here, but from a stipulation in Ethiopian army regulations.

2d Lt. Zeleko Goshu, at 33 a 19-year army veteran, explained: "If we are killed, our families receive half-pay for six months, but nothing if we are captured."

So he is afraid to write his wife and five children lest they lose the half-pay - $133.50 a month in his case, $45 for a recruit - even though they may think he is dead.

He and the others interviewed were captured in early January only half an hour after they were helicoptered into beleagured Om Hager, just inside Eritrea near its border with Sudan and Ethiopia.

Under increasing Eritrean guerrilla pressure part of the garrison had gone over to the rightest Ethiopian Democratic Union, the major group opposing the Marxist military government in Addis Ababa.

The lieutenant was to help lead the other troops north to the larger Ethiopian army outpost in Tessenai, when his unit was ambushed. More than 45 Ethiopians were killed.

Now the prisoners worry about their fate. Even being freed - a distinct possibility - is not without risk.

"If we return to the army," a young soldier said, "we know they [his army superiors] wil; l kill us because we surrendered with our weapons."

Left unsaid were the Ethiopian government's fears of ideological contamination, for the prisoners of war are released only after a strong dose of political indoctrination. Mixed in between physical training, football matches every other day and the dull prison routine are four intensive political education lessons every week.

The thrust of the lessons is that Eritrea is a nation, not a secessionist province and deserves to be independent. A corollary is that the Ethiopian military government led the prisoners astray.

Some of the lessons are illustrated with quotations from Marxist leaders, an ironic twist since the ELF is not officially Marxist while Ethiopia's present leadership is.

"The dergue [the ruling military committee] told us nothing when we were sent to Eritrea," a veteran sergeant said, "but we heard rumors the ELF were very cruel assassins. But they treated us like brothers and shared what they have with us," he added in a diplomatically phrased allusion to the spartan conditions captors and captives share in this dusty, rock-strewn semi-desert in western Eritrea.

The Eritreans have told the prisoners about the existence of the Ethiopian People's Revolutionary Party and the Tigre People's Liberation Front, leftist opposition groups just south of Eritrea in northern Ethiopia. The two organizations receive ELF arms and support.

Late last year, 44 Ethiopian soldiers led by a lieutenant colonel deserted their units, spent 2 1/2 months in political education with the ELF and were later allowed to join the EPRP.

Early this year, 580 survivors of the ill-fated "red march" - the dergue's aborted plan to march more than 100,000 poorly armed Ethiopian peasants through Eritrea last May - were released after political indoctrination.

The peasants apparently drifted back to their villages - something many of the present prisoners would like to do if it were not for fear of the dergue's retribution.

A member of the ELF's 41-member Revolutionary Command said the object of the political education is simply to show the prisoners that "we are not their enemies, that our cause is just and that we are not bandits."

Mindful of the Geneva Conventions governing prisoners of war - if oblivious to the prohibition of political indoctrination - he insisted that he prisoners had been forwarded to the International Committee of the Red Cross in Geneva through the Eritrean Red Cross and Red Crescent.

But the prisoners' main concern, voiced by the lieutenant, was "our great desire to leave this place before we go crazy."

"We are very fearful of the Ethiopian air force's (American-manufactured) F-86s and F-5Es," which regularly fly over the prison on their way to relieve pressure on the beleagured Ethiopian garrisons bottled up in towns and cities by the Eritreans.

Caught between their fears about returning home and their desire to escape the rigors of POW existence, the Ethiopian troops here expressed a willingness to have EPRP leaders visit them.

Better to be among fellow Ethiopians, even if they are Marxists, the soldiers seemed to think, rather than rot here. For the ELF, anything weakening the dergue was justified.