Former military strongman Field Marshal Praphas Charusathien, who returned from three years of political exile a week ago, says he is "an old man" who wants to live out his remaining years quietly in his homeland.

But the actions of the 65-year-old ex-director and the homage paid him since his return from Taiwan Jan. 8, leave little doubt that he is again a force in Thailand's turbulent political life.

Already, Thai and foreign observers are describing Praphas as "the most powerful man in the country." It is anticipated that he ill exercise a powerful influence over the military-backed government that seized power Oct. 6 and cleared the way for his return.

Prime Minister Thanin Kraivichien, an appointee of the military has been treading on the toes of free-wheeling senior officers with his puritanical ideas. A number of political observers expect Thanin to be replaced in the next few months. Some of these observers believe Praphas would be the army'stop choice as a replacement, but others believe he will operate from behind the scenes.

But as he spoke to about 100 reporter at his palatial residence here, Praphas said nothing could be further from the truth. Asked what his plans were, he replied, "Anything I can do to help the country I will do, but as for politics -enough."

Implying that he is a poor man, Praphas said he would live on his military pension alone his first priority is "a find-food-to-eat project." He said that he was not even sure whether he still owned his home. This was a reference to the fact that the vast house, together with his fleet of automobiles, pleasure boats and other property were confiscated by the government when the military dictatorship headed by Praphas, former Prime Minister Kittikachorn was ousted in October, 1973.

The new government has cleared the trio of all blame for the deaths of at least 70 students in the rebellon and there is little doubt that the former official's property will be restored.

Praphas had tired to return to Thailand once before, on Aug. 19, but following student rioting, during which two student were killed, the government made him leave again.

One month later, Thanom entered the country from his exile in Singapore and immediately was ensconced as a Buddhist monk in a temple under the patronage of Thailand's royal family.

This triggered another student demonstration that turned into a bloody battle between police and students, the collapse of the civilian government and the coup by military officers.

The role of the Thai royal family in th coup is a subject of much conjecture among Thais and foreign observers in Bangkok. Because criticism of royalty is a serious crime here, however, it is never discussed publicly.

I is clear, though, that both Thonom and Praphas were able to return to Thailand only after King Bhumibol Adulyadej granted permission. Thanom's son Narong, who is married to one of Praphas' three daughters and is reportedly disliked by the king, remains in exile in West Germany.

As one indication of the power Praphas once again commands, he was granted an audience by the king on Jan. 12. Asked what was discussed, Praphas replied. "The King asked me how I was and he told me about the situation in the past (during Thailand's three-year experiment with democratic government), about how disordered it was."

He added that the audience was arranged "by mutual request."

Although he was one of the principal architects of the arrangements which allowed the United States to base thousands of troops at Thai airbases and operate bombing missions in Vietnam during the war there, he said that he approaved of the U.S. withdrawal, which was completed last July.

He added, however, "I don't agree with the withdrawal of military aid, it's damaging to us." Defense Minister Adm. Sangad Chaloryu announced on Nov. 29 that Thailand would not seek further U.S. military aid once the current program expired this year.

Since the current government seized power, Thailand has renewed its allegiance to theUnited States and halted efforts by the civilian government to improve relations with the neighboring communist-ruled states of Vietnam, Cambodia and Laos.

Several senior officers have accused Vietnam and Laos of fueling the Thai unsurgency. Asked for his opinion of Thailand's relationship with its Indochinese neighbors, Praphas replied, "Veru risky. All these neighbors have changed. We must bevery careful. It's dangerous."