Bangkok (AFP) - Chinese fighter jets thunder through blue skies above an air force base in northeast Thailand, a symbol of the blossoming military and political ties between the junta-run country and its authoritarian northern neighbour.

For the last two weeks Thai and Chinese planes have been taking part in the inaugural joint air force drill, an exercise culminating later this week with a performance by Beijing's acrobatic air team.

For Group Captain Chanon Mungthanya, a Royal Thai Air Force spokesman involved in the drill at Korat, it is a valuable opportunity to interact with his Chinese counterparts.

"Our relationship will go up a level during this exercise," he told AFP.

Historically, Thailand has been one of Washington's staunchest military allies in Southeast Asia and could have expected to see that relationship blossom under US President Barack Obama's "pivot" to Asia.

But the May 2014 coup, the second in the last decade, and the junta's subsequent rights crackdown has strained those ties.

Meanwhile Thailand is doing a pivot of its own.

"The junta is obviously much more comfortable with China because they speak the same language and commit the same practices: authoritarianism," said Puangthong Pawakapan, a Thai politics expert at Chulalongkorn University.

- China critics deported -

Beijing swiftly recognised junta chief General Prayut Chan-O-Cha and is pushing plans for a multi-billion dollar Chinese-built rail network through the kingdom.

Thailand is also considering whether to spend $1 billion on Chinese submarines.

But rights groups say this closeness has unpleasant consequences inside Thailand, with the junta seemingly happy to do Beijing's dirty work.

In July more than 100 Uighur refugees were deported to China, despite warnings from the United Nations that the Muslim minority faced the risk of persecution.

Thai authorities insist the deadly August Bangkok shrine blast was not a revenge attack, even though the majority of victims were ethnic Chinese and two Uighurs have been charged.

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Three weeks after those deportations, in comments that caused much media merriment, Thailand's then foreign minister General Tanasak Patimapragorn lavished praise on Chinese foreign minister Wang Yi.

"If I were a woman I will fall in love with his excellency," he said.

Earlier this month two Chinese dissidents who had been granted refugee status by the UN, one of whom had been living in Thailand for years, were abruptly arrested and sent to Beijing. A third has gone missing in Thailand.

"Thailand is no longer a safe place for anyone with anti-CPC (Communist Party of China) views," professor Puangthong said.

Paul Chambers, director of the Institute of South East Asian Affairs, said the junta is "playing the realist... juggling connections with China, Japan and the US to obtain the highest dividend for the Thai state".

But Chambers believes the recent deportations are something new.

"It does show the Chinese that the Thai military is willing to take enormous flak to help Beijing out."

- Delicate balance for US -

For the United States, events in Thailand create a quandary.

Obama has made reasserting American influence in the Asia-Pacific region a flagship of his foreign policy.

But the "pivot" has fallen victim to diplomatic distractions in the Middle East and other trouble spots.

It has also struggled to gain traction at a time when democratic progress across Southeast Asia shows signs of stagnation.

Thailand chafes under a junta seemingly in no rush to hold elections. Cambodian strongman Hun Sen retains his grip after more than 30-years of rule. Vietnam and Laos remain intolerant one-party states.

Washington cancelled some military aid after the Thai coup and continues to call for a return to democracy. But it is also wary about pushing away a regional ally.

Earlier this year it pressed ahead with the Cobra Gold exercise, Asia's largest military drill, conducted annually in Thailand.

"Thailand has pivoted toward China but Bangkok's edging toward Beijing is not at all a total plunge," said Chambers.

Washington, he says, still holds significant influence, especially if the recently agreed Trans-Pacific Partnership becomes a reality and Thailand chooses to join.

A spokeswoman at the US embassy in Bangkok said Washington's close relationship with Thailand has "endured and flourished through many challenging times".

"This does not prevent us from addressing issues of concern, including about democracy and human rights," she said.

Back on Korat airbase, new friendships between Thai and Chinese soldiers are being forged.

"We can chat, we can have our military help each other out," said Group Captain Chanon. "We eat together, get to know one another, become tired and practise together".