Relaxed and cheerful as Sunday picnickers, yet another chartered planload of mostly American oil technicians' families flew out Thursday as part of a growing tide of foreigners leaving Iran, its strikes and political crisis.

Symptomatic of their calm mood was the presence of technicians taking advantage of the charter to Bahrain to start regular leaves which had been upset by the week-long strike by Iran Air, the national carrier.

Other technicians had flown in from the Persian Gulf island state of Bahrain to report back to duty at the Ahwaz headquarters of the strike-bound National Iranian Oil Corp. or at drilling rigs throughout the coastal province of Khuzestan.

"I sure hope I can make it in time to see my son Russ play in the football game for Slippery Rock," said Paul E. Grimm, general manager of the oil service company which works for the Iranian oil company "It's the last game of the season."

Whatever the reported near panic in Tehran and other Iranian cities, the foreigners working in Khuzestan are another breed - "simple country folk with their feet on their ground" as one man put it.

Mrs. Linda Hall, sending her 11-year-old daughter, Missie, and 13-year-old son, Mike, off to grandmother in Lubbock, Tex., was in a wistful mood.

"When we went on vacation this summer," said Mrs. Hall, the wife of a turbine specialist, "we planned to stay here for another four to six years."

Mrs. Caroline Hill, a 10 year veteran of Ahwaz leaving with her four teenage children, said her husband Jerry came home last week and said, "You and the kids are leaving."

"I don't know when, but I'm confident we're coming back," she said. "Why everything I have is in my six bedroom house in Ahwaz. I don't even own a coffee cup back in Oklahoma City."

"My kids have never seen snow, never been with their families for Thanksgiving or Christmas, never been but to this one school," Mrs. Hill said, mentally balancing the pros and cons of her departure.

Next to her stood a woman cluthing a baby, another wearing a fur coat despite the autumn heat and a third holding a plastic carrying case containing an excited daschsund.

Yet, despite the increasingly commonplace departure scenes, so far no foreign oil experts are known to have given up their jobs and left the country because of the crisis before their contracts expired.

And despite the express demands of striking oilfield workers' that all foreign workers be ousted, no foreigners appear about to comply. To do so would sharply undercut the government, which relies on their expertise to keep Iran the world's second-ranking oil exporter after Saudi Arabia.

Simple prudence - rather than any systematic harassment - dictated the foreign oil workers' decision to move their families out.

They consider themselves the lucky ones - either self-employed or working for private companies. Of roughly 1,000 Westerners working in oil-related business in the province, 560 are employed by the operating services branch of the Iranian firm and have not been authorised to send their families out.

But attendance statistics at the special school for foreigners here tell the story - since early October, 116 children have left and only 14 have arrived.

In the past week, families have been evacuated by a variety of private companies - Reading and Bates, Sante Fe and Sedco, among the Americans, for example.

Besides the claustrophobic effect of the Iran Air strike, other factors cited are the hostile environment of recent months and the now three-week-old strike by oil workers, which has had antiforeign, especially antiAmerican, overtones.

Moreover, many foreigners said that their once carefree life style had evaporated with the imposition of martial law in early September.

"First they firebombed the Kien Pars nightclub and the El Chico restaurant," a young British technician said, "and that ended whatever nightlife we had."

"The wives stopped going downtown to buy vegetables in the bazaar," he added , "but the supermarket, the power, water and gas still works so it was not so much that we were suffering as the fact that we felt confined." The city is subject to a midnight-to-5 a.m. curfew.

"Going into town for the last two months has been taboo," he said.

When children brought back the first anti-American pamphlets, the technician said, "we didn't take them seriously."

Apparently the same tracts as seen elsewhere in Iran, they warned: "Yankees, go home by December 1 if you don't want to get killed."

Moreover, a series of minor incidents began worrying the foreigners.

An oil company helicopter was stoned by villagers when it made an emergency landing near a village.

Gardon Cameron, president of the Los Angeles-based Santa Fe Drilling Co., had his car stoned and jostled during a field inspection visit.

Breaking and entering and theft has been on the increase with police unable to stop the trend. At Bushihr, the homes of four or five families working for the Schlumberger seismological research firm had their windows broken.

All this led the companies to dust off contingency plans for evacuation.

"And," a veteran said, "we all started listening to the radio news a lot more carefully."

"Yet, if you stay out of the middle of town," where Scorpion light tanks, M-113 armored personnel carriers and machine gun-mounted jeeps patrol, a technician said, "you could say nothing is going on. If you don't have your ears open, you'd never know anything is going on here."

"The funny thing is that really there is nothing to cause us any major concern about our safety," he added, "but just because the situation is very calm does not mean it couldn't change in the next five minutes."

Many of the departing families appear genuinely concerned about their Iranian friends. "They cannot just get up and go like us," said an American technician.

And as one woman said in reflecting a seemingly general sentiment: "The strikers say they want us all out, and I know it sounds awful to say but if we leave the oil fields would stop functioning at full tilt."