BANGKOK, Thailand (AP) _ Souphanouvong, the ''red prince'' of Laos who led communist guerrillas and renounced his royal title, has resigned as the nation's president, official Laotian radio reported.

A transcript of the broadcast, obtained Friday from a Western embassy that monitors the radio, said the decision was based on ''requirements'' of the December 1975 communist revolution and Souphanouvong's ''proposals on his physical condition.''

Souphanouvong, the only president communist Laos has had, is 74 and has been ill with high blood pressure, said a senior official at the Laotian Embassy, who spoke on condition of anonymity.

He was treated in Moscow for more than a month after he fell ill while attending the September summit in Zimbabwe of nations that profess non- alignment, the source said.

In the broadcast Thursday, the official radio said Phoumi Vongvichit, a member of the Pathet Lao Communist Party Politburo and a vice chairman of the council of ministers, was appointed acting president. It did not say when a permanent occupant of the largely ceremonial post would be named.

The radio did not way whether Souphanouvong would keep his membership on the powerful Politburo.

Despite his prominence, Souphanouvong is thought never to have exercised power approaching that of Kaysone Phomvihane, party secretary-general and prime minister of the impoverished, landlocked nation of 3.6 million people.

Prince Souphanouvong renounced his title and became the first head of state when the Pathet Lao took control, forced the king to abdicate and declared Laos a republic in 1975. It became a close ally of Vietnam and the Soviet Union.

He was born in the royal capital of Luang Prabang in 1912, the 20th and youngest son of Prince Boun Khong, the ruling viceroy.

Souphanouvong and his half-brother Souvanna Phouma emerged as leaders, the one opting for revolution and the other for a gradual approach to independence from France.

When the French returned to Laos after World War II and granted limited autonomy, Souphanouvong belonged to the Lao Issara (Free Laos) movement that generally was prepared to work with the colonial master.

His ties with Vietnamese Communist leader Ho Chi Minh alarmed more moderate nationalists, however, and Free Laos expelled him in May 1949.

The prince returned to the hills, where he had organized guerrilla raids on French garrisons, and in 1950 helped found the Pathet Lao, or Lao Nation. It joined forces with the Vietnamese against the French.

Pathet Lao forces became increasingly strong in northeastern Laos from 1950-54, when the Geneva conference ended the first Indochina war.

Souvanna Phouma became prime minister, but when the 1958 elections showed significant support for the Pathet Lao, the right wing overthrew him and jailed Souphanouvong for 15 months. Souphanouvong escaped. A civil war ensued and Souvanna Phouma formed a new government in 1962 including the Pathet Lao, moderate and right-wing forces, but the fragile coalition was shattered by the widening war in Vietnam.

Vietnamese communists, seeking to protect the Ho Chi Minh supply trail running through eastern Laos, supported the Pathet Lao and the Americans aided the goverment. Souvanna Phouma authorized U.S. air strikes on Pathet Lao positions in 1964.

Another coalition government was formed in 1974 but the Pathet Lao ousted the rightists and seized full control in December 1975, eight months after the communist victories in Cambodia and Vietnam.

Souvanna Phouma died in Vientiane, capital of Laos, in 1984.