BANGKOK, Thailand -- Eighteen years after a military coup toppled one of Thailand's most politically powerful leaders, former prime minister Thaksin Shinawatra walked free on parole, finishing six months in a police hospital and sparking fears he now shares power with his party's pliant prime minister.

"There is only one prime minister under the constitution. That's me," their Pheu Thai party's less popular Prime Minister Srettha Thavisin insisted to reporters hours after Mr. Thaksin was freed on February 18.

Some warn that Mr. Thaksin, 74, is so influential and Machiavellian that this Southeast Asian, Buddhist-majority nation now has "double prime ministers".

"Thai society now knows that Thaksin is the shadow prime minister with real power," Wanwichit Boonprong, a Rangsit University political science lecturer, said in an interview.

Mr. Thaksin's six-month hospital incarceration and parole also sparked complaints.

"Even though he [was] a prisoner, he has received special medical treatment privileges in the police hospital without ever having been in prison for a single day," Mr. Wanwichit said.

"The Thaksin case has sadly stigmatized the justice system," the Bangkok Post said in a February  17 editorial.

"As he walks away a free man, the justice system's credibility will sadly be in freefall," the paper said.

Prime Minister Srettha, a former real estate mogul, leads a civilian-military coalition government with a 250-member military-appointed Senate and three elected military-allied political parties.

That arrangement appears to please the U.S.-trained military which is involved in protecting its withering political power and lucrative commercial enterprises, including racecourses, boxing stadiums, golf courses, shops, restaurants, radio and TV stations, an electric power station, and hotels in barracks.

Mr. Srettha, who doubles as finance minister, is apparently content focusing on the vulnerable economy and acting as Thailand's salesman, while leaving the trecherous tricky-track intrigue of politicking to Mr. Thaksin.

Mr. Thaksin is de facto leader of their Pheu Thai (For Thais) party, which is nominally headed by his daughter Paetongtarn Shinawatra.

"He [Thaksin] hasn't seen the air and sun outside for 180 days," Ms. Paetongtarn said on Instagram on February 18.

She and her sister Pintongta posted a photo of the freed Mr. Thaksin poolside, wearing a neck brace, with his arm in a black sling.

Mr. Thaksin is expected to play a more active role in his party, which evolved from previous family-run incarnations after he founded the Thai Rak Thai (Thais Love Thais) party in 1998.

"I may have to warn the government not to create the circumstance of double prime ministers," said opposition Move Forward Party (MFP) leader Chaithawat Tulathon.

Mr. Thaksin's release is widely expected to boost the political influence of the ruling military, royalists, and conservatives.

They appear to need the elderly billionaire politician as a shield against a young generation of MFP reformists in parliament who want to reduce the military's powers, end conscription, and break up business monopolies.

The MFP also want to weaken the royal defamation law Section 112 and its punishments of up 15 years imprisonment.

Ironically, Mr. Thaksin himself faces a criminal charge of lese majeste, and an equally severe "computer crime" charge, for allegedly expressing statements in 2015 about the constitutional monarchy's advisors and Thailand's political instability.

The Office of Attorney-General's (OAG) is considering the former attorney-general's decision to indict Mr. Thaksin for violating 112. He denied the charges.

On Monday February 19, Mr. Thaksin arrived in a wheelchair at the attorney-general's office, which requested more details about his case, scheduled another meeting with him on April 10, and released him on a $14,000 bail.

Despite those lingering animosities, the army generals who led the 2006 coup against Mr. Thaksin -- and a 2014 putsch ousting the government of his sister, then-prime minister Yingluck Shinawatra -- appear to be tacitly embracing Mr. Thaksin.

Ms. Yingluck, 56, fled abroad dodging a five-year prison sentence for dereliction of duty while prime minister overseeing and accounting for major projects.

She is expected to soon return to Thailand with a relaxed sentence, if her father's political rehabilitation succeeds.

"The conservatives, who do not have much choice, must compromise with Thaksin and the Pheu Thai Party to gain power," Mr. Wanwichit said.

"The conservative political parties did not have a political leader with sufficient charisma," Mr. Wanwichit said.

Mr. Thaksin would not become a political candidate, analysts said.

"With the Srettha government in office, Thaksin can work behind the scenes and act as Srettha's puppet-master," Paul Chambers, a specialist in Thai politics at Naresuan University, said in an interview.

"What Thaksin cannot do is anger the king. He also cannot ever be prime minister again.

"He would act through cronies such as Srettha, or his relatives such as his daughter [Paetongtarn].

"Thailand today is a civilian-led military-backed highly defective democracy," Mr. Chambers said.

Former foreign minister Kasit Piromya said of Mr. Thaksin: "For the past 20 years, he has been dominating and influencing Thai political life in no small measure, whether living in the country or abroad.

"Thaksin is being treated by the establishment as a comrade of arms against the left -- or republicanism thinking. It is difficult to guess the duration of this marriage of convenience," Mr. Kasit said in an interview.

Mr. Thaksin's willingness to unite with the military, royalists, and their conservative allies, angered many of his anti-military Red Shirt supporters.

More than 90 people -- most of them civilians and Red Shirts -- were shot dead during clashes with the military in a nine-week Bangkok insurrection in 2010.

The Reds vainly tried to bring back their fugitive hero because Mr. Thaksin symbolized their democratic struggle against military rule.

"There is a strong belief that Thaksin remains highly influential in the Pheu Thai party, even though he has lost substantial support from members of the Red Shirts," Kantathi Suphamongkhon, a foreign minister in Mr. Thaksin's administration from 2005 to the 2006 coup, said in an interview.

Swathes of rural voters favored Mr. Thaksin because his populist policies offered cheap loans, virtually free health care, scholarships, village development projects, and other assistance to neglected Thais.

His opponents portrayed him as a greedhead, manipulating his politics so his family could rake in cash from allegedly sketchy deals.

During Mr. Thaksin's 2001-2006 prime ministry, President Bush welcomed him to the White House after Bangkok assisted Washington in its international "war on terror".

"Thailand was one of at least 54 nations to participate in the CIA’s program of 'extraordinary rendition' wherein at least 136 terror suspects were sent to 'black sites' for interrogation and torture by Americans," wrote Benjamin Zawacki, Bangkok-based American author of "Thailand: Shifting Ground Between the U.S. and a Rising China".

"Thailand was one of eight nations to host at least one such site," Mr. Zawacki said.

Relations between Washington and Bangkok tightened, and President Bush designated Thailand as a non-NATO ally of the U.S.

Washington criticized the 2006 military coup against Mr. Thaksin, paused some military programs, but has since restored and sought to improve ties with Bangkok.

Mr. Thaksin fled in 2008 and spent 15 years as an international fugitive dodging eight years in prison, convicted in three cases.

The court said his crimes included ordering Thailand's Export-Import Bank to grant a lower interest $114 million loan to Myanmar's military regime in 2004, so it could buy his family's Shin Satellite products, the Bangkok Post reported.

The Supreme Court separately convicted him of launching a nationwide lottery during 2003-06 without authorization.

He was also guilty of malfeasance and conflict of interest for links to stock shares in the government's telephone concessionaires.

Mr. Thaksin meanwhile bounced among Dubai, London, Hong Kong, and Singapore, consulting with colleagues and trying to boost supporters' morale.

In a 37-page statement in 2007, the new coup leaders explained why they were "restoring democracy".

"The narcotic suppression campaign of the previous [Thaksin] government had led to a large number of extrajudicial killings, approximately 2,500 deaths," said the junta, calling itself a Council for National Security.

Those killings "constituted a serious violation of human rights of a scale unprecedented in a Buddhist society like Thailand," their statement said.

"Former prime minister Thaksin's actions or speeches verging on lese majeste against the monarch on a number of occasions were poignant to those who heard or witnessed them, and subsequently resulted in many complains reported," the coup leaders said.

Their "documents" justifying their 2006 coup were illustrated with photos of them meeting Thais and foreigners, including U.S. embassy diplomats and military officers flanked by small American and Thai national flags.

Thailand's current crisis began in August when Mr. Thaksin returned to Thailand, grinning in Bangkok's international airport.

He spent less than 12 hours in Bangkok Remand Prison before being whisked to to downtown Bangkok's Police General Hospital for what officials described as critical conditions including chest pain, hypertension, and low blood oxygen.

Prison officials and the hospital refused to release Mr. Thaksin's "confidential" medical reports.

In a stunning reversal of fortune while on the hospital's 14th floor, the court reduced his prison sentences to eight years, and the king granted him a pardon, leaving Mr. Thaksin with only one year to serve, ending in August 2024.

But after six months, he qualified for parole because he was older than 70, suffered severe health problems, and served half of his sentence.

After being released, Mr. Thaksin's family took him to their residence on Bangkok's outskirts. 

Mr. Thaksin is believed to be grooming his politically inexperienced daughter Paetongtarn, 37, to replace Mr. Srettha as prime minister.

Their Pheu Thai-led coalition includes the military-dominated Palang Pracharath Party and United Thai Nation Party -- two main groups in the previous regime installed by the 2014 coup against Ms. Yingluck.

The pro-military Bhumjai Thai party is also a key coalition member.

"These three parties can be considered strict guardians of the interests of the military and monarchy," wrote columnist Thitinan Pongsudhirak, a political science professor at Bangkok's Institute of Security and International Studies.

Panic erupted among the establishment in May when the MFP, led by Pita Limjaroenrat, scored 14 million votes, scooping 38 percent of the total votes in nationwide parliamentary elections.

Mr. Pita's vociferous anti-112 stance resulted in his rejection for the prime ministry by the military-appointed Senate and their royalist allies in the House.

Mr. Pita now languishes in the opposition, facing possible charges of lese majeste for criticizing 112 during his campaign.

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Richard S. Ehrlich is a Bangkok-based American foreign correspondent reporting from Asia since 1978. Excerpts from his two new nonfiction books, "Rituals. Killers. Wars. & Sex. -- Tibet, India, Nepal, Laos, Vietnam, Afghanistan, Sri Lanka & New York" and "Apocalyptic Tribes, Smugglers & Freaks" are available at
https://asia-correspondent.tumblr.com