Pridi retired from the regency when King Ananda Mahidol returned in December 1945.
He was formally named a Senior Statesman (Ratthaburut Awuso), and served as an advisor to the post-war, civilian governments of Thawi Bunyaket and Seni Pramoj.

In March 1946, Khuang Aphaiwong, who had been elected prime minister in January, resigned.
Pridi assumed the position in an attempt to stabilize the political situation, now spiraling out of control.
It was during the first months of the Pridi government that the war crimes trial of Phibun was dismissed on a legal technicality.

On the morning of 9 June 1946, the young king was found dead in his bed in the Baromphiman Mansion in the Grand Palace.
The monarch's died from a gunshot to his head.
In October 1946, a commission of inquiry ruled that the king's death could not have been accidental, but that neither suicide nor murder was satisfactorily proved.
Sulak Sivaraksa, a prominent conservative and monarchist, wrote that Pridi's role in the event was he protected a wrongdoing royal, and prevented an arrest of a person who destroyed the evidence.

After a general election, Pridi resigned as prime minister, resumed his status of senior statesman, and left on a world tour, visiting Generalissimo Chiang Kai-shek and US President Harry S. Truman along the way.

On 8 November 1947, army troops seized various government installations in Bangkok.
The coup, led by Lieutenant General Phin Choonhavan and Colonel Kat Katsongkhram, ousted Thamrong's government.
It marked the return to power of Phibun.
At the same time, armoured cars arrived in front of Pridi's riverside residence.
When the troops entered they found that Pridi had departed.
Pridi spent a week hiding with the Royal Thai Navy at Admiral Sindhu Songkhramchai's headquarters.
On 20 November, he was spirited to Singapore by British and US agents.

Phibun arrested King Ananda's secretary, Senator Chaleo Patoomros, and two of his pages under charges of conspiracy to kill the king.
Rumours were spread that Pridi was part of a conspiracy involved in the alleged regicide, and that he had plans to turn Thailand into a republic.
After a farcical trial, during which the entire defense team resigned and two members of a subsequent team were arrested under charges of treason, the judges ruled that none of the accused could have fired the fatal shot.
However, it did convict a royal page, Chit Singhaseni, of being a party to the crime.
Chit appealed his conviction.
The appeals court later dismissed Chit's appeal and, undeterred by the legal doctrine of double jeopardy, found another page, But Pathamasarin, also guilty.
The supreme court upheld the convictions, convicting Chaleo as well.
All three were executed several years later.

Biographer William Stevenson has said that King Bhumibol Adulyadej did not believe that Pridi was involved in his brother's death.

Pridi supported the Vietnamese independence movement of Ho Chi Minh.
As the cold war infected the post-war arena of Southeast Asia, Thailand became a focus of the US and the USSR.
In 1949, when China turned communist, the Viet Minh fought the anti-French war.
The US doubted that Pridi would support the communist movement in the region, but his policy was controversial, leading to the coup which ousted him from power by his former ally, the wartime leader Plaek Phibunsongkhram.
Pridi retired from the regency when King Ananda Mahidol returned in December 1945. He was formally named a Senior Statesman (Ratthaburut Awuso), and served as an advisor to the post-war, civilian governments of Thawi Bunyaket and Seni Pramoj.
In March 1946, Khuang Aphaiwong, who had been elected prime minister in January, resigned. Pridi assumed the position in an attempt to stabilize the political situation, now spiraling out of control. It was during the first months of the Pridi government that the war crimes trial of Phibun was dismissed on a legal technicality.
On the morning of 9 June 1946, the young king was found dead in his bed in the Baromphiman Mansion in the Grand Palace. The monarch's died from a gunshot to his head. In October 1946, a commission of inquiry ruled that the king's death could not have been accidental, but that neither suicide nor murder was satisfactorily proved. Sulak Sivaraksa, a prominent conservative and monarchist, wrote that Pridi's role in the event was he protected a wrongdoing royal, and prevented an arrest of a person who destroyed the evidence.
After a general election, Pridi resigned as prime minister, resumed his status of senior statesman, and left on a world tour, visiting Generalissimo Chiang Kai-shek and US President Harry S. Truman along the way.
On 8 November 1947, army troops seized various government installations in Bangkok. The coup, led by Lieutenant General Phin Choonhavan and Colonel Kat Katsongkhram, ousted Thamrong's government. It marked the return to power of Phibun. At the same time, armoured cars arrived in front of Pridi's riverside residence. When the troops entered they found that Pridi had departed. Pridi spent a week hiding with the Royal Thai Navy at Admiral Sindhu Songkhramchai's headquarters. On 20 November, he was spirited to Singapore by British and US agents.
Phibun arrested King Ananda's secretary, Senator Chaleo Patoomros, and two of his pages under charges of conspiracy to kill the king. Rumours were spread that Pridi was part of a conspiracy involved in the alleged regicide, and that he had plans to turn Thailand into a republic. After a farcical trial, during which the entire defense team resigned and two members of a subsequent team were arrested under charges of treason, the judges ruled that none of the accused could have fired the fatal shot. However, it did convict a royal page, Chit Singhaseni, of being a party to the crime. Chit appealed his conviction. The appeals court later dismissed Chit's appeal and, undeterred by the legal doctrine of double jeopardy, found another page, But Pathamasarin, also guilty. The supreme court upheld the convictions, convicting Chaleo as well. All three were executed several years later.
Biographer William Stevenson has said that King Bhumibol Adulyadej did not believe that Pridi was involved in his brother's death. 
Pridi supported the Vietnamese independence movement of Ho Chi Minh. As the cold war infected the post-war arena of Southeast Asia, Thailand became a focus of the US and the USSR. In 1949, when China turned communist, the Viet Minh fought the anti-French war. The US doubted that Pridi would support the communist movement in the region, but his policy was controversial, leading to the coup which ousted him from power by his former ally, the wartime leader Plaek Phibunsongkhram.
Pridi Banomyong