Gen. Mohammed Zia ul-Haq has the stocky, muscular build of the tank commander he once was and likes to picture himself as a simple, patriotic soldier eager to shed the absolute power he now wields in Pakistan.

"I and my colleagues have no intention to remain in politics," he said, chatting easily at his spacious villa here.

Zia is reminded that another pair of generals, Ayub Khan and Yahya Khan, had also once seized power in Pakistan and did not give it up until they were forced out.

"This martial law is different," he insists, flashing a broad smile surmounted by a bristling black mustache.

"We have not abrogated the constitution. I sit here," meaning that he occupies the house assigned to the army chief of staff, "not there," pointing to the vacant prime minister's residence. "I wear an army uniform."

He readily acknowledges however, that an obliging supreme court has set aside the constitution's guarantee of rights to make his martial law orders supreme. It is only a short distance to the house vacated by Zulfiqar AL Bhutto, the prime minister Zia deposed last July.

More significantly, a key Zia adviser, retired Maj. Gen. Farman Ali has been writing about how difficult it is for a military administration to hand over power to civilians and hinting that Zia is the best man to lead the country.

"I've got to make damn sure that the elections bring in . . . a party or group of parties" that will "win elections fairly and squarely and they should be stable enough" to rule for several years, Zia says.

Who will decide when such conditions will be fulfilled?

"Me and my colleagues" is the reply.

The general's formal title is Chief Martial Law Administrator, CMLA. But he has postponed promised election dates so frequently that this acronym has now been translated - in private conversations - as Cancel My Last Announcement.

Zia, however, is not a devious man. There is every reason to think he believes what he is saying at the moment he says it. The trouble is that the hierarchichal life of 33 years as an army officer does not equip many men for the subtle and complex task of ruling 70 million people, most of them miserably poor and a handful extraordinarily rich.

The general appears to be a man of simple, almost spartan tastes and is undeniably a devout Moslem. His walls are covered with embroidered or embossed verses from the Koran and praise of Allah. He does not drink and is rigorously enforcing the prohibition that whiskey-loving Bhutto introduced just before he fell in a futile bid to curry favor with the ulemas (Moslem religious leaders.)

Zia makes no concessions on this score. The other night, he was a gracious host at a dinner for Nelson Rockefeller, his wife, and a few other Americans with less abstemious tastes. Cocktails in the large garden consisted of Coca Cola and lime juice. Water, not wine, was on the table. Zia's only indulgence appears to be British cigarettes, which he presses on guests along with an almost embarassing array of gifts.

Like so many generals who have seized power in the Third World, he has been trained in an admires the United States. Zia has taken the armored school course at Ft. Knox and graduated from the command and general staff school at Ft. Leavenworth. His son Ajaz, at 25 the oldest of Zia's five children, studied at Southern Illinois University in Carbondale and will soon come to Washington for a job in the private International Bank.

Zia, 54, is very much the family man. While he talks to a guest in his living room, his daughter Zain, 4, shyly pokes her head through the door.

But his delight in Americans does not extend to President Carter's opposition to a projected French sale of a nuclear processing plant that could give Pakistan weapons-grade plutonium.

Why should nuclear nonproliferations begin with Pakistan, he argues heatedly. "The West has got it - the East has got it - India - the Jews have got it - why should Pakistan be deprived of this technique?"