In an op-ed piece of May 21, Jeane Kirkpatrick alluded to the visit of Tunisia's President Zine El Abidine Ben Ali to Washington -- four times spelling his name ''Ben Ami'' -- and questioned his "manner of arriving in power" and "of retaining it." His accession on Nov. 7, 1987, was done in total conformity with our constitution. Under Article 57 and based on a medical statement signed by seven attending physicians determining that the former president was no longer able to discharge his duties, then-prime minister Zine El Abidine Ben Ali was sworn in as president.

Declaring his commitment to lay the foundation of a democratic system, he did not wait for the end of the term, due to expire in 1991, but called for early general elections, which were held on April 2, 1989. No opposition party fielded a candidate for president; as co-signers of "The National Pact," all chose to support Mr. Ben Ali. An overwhelming majority voted for him in elections that independent observers found free, fair and open.

I also wish here to reply to an advertisement in The Post of May 15 from the ''North African Students for Freedoms'':

Tunisia does not fire opposition members, revoke passports of ''thousands of people'' or engage in ''systematic police brutality and torture of political prisoners.'' My government stands ready to provide information on any case and welcomes any human rights organization.

Far from being ''moderate,'' the fundamentalist ''Ennahdha'' movement calls for negating women's rights and closing Tunisian society to Western cooperation.

The U.N. Convention Against Torture, to which this group calls Tunisia to adhere, was signed and ratified by Tunisia in 1988 -- without any reservation.

As stated by President Ben Ali and corroborated by independent observers, there are no political prisoners left in Tunisia. Since Nov. 7, 1987, more than 12,000 prisoners have been released, and in 1989 the parliament adopted a general amnesty. The case of M. Ben Salem, to which the advertisement refers, is before the courts. He is entitled to due process and equal protection.

All legal political movements have been permitted to organize as parties. ''Ennahdha'' has so far refused to abide by the law on political activities, and its program, based on religion, is in open violation of the law, but it has been granted a permit and publishes its own newspaper.

As for the 500 students who forfeited their exemption from military service by engaging in activities unrelated to their studies, most have since been allowed to resume their studies.

ABDELAZIZ HAMZAOUI Ambassador of Tunisia Washington