Here’s a twist in the American network of Indo-Pacific defenses against Communist China that defies belief even in a world of shifting loyalties and ambiguous friendships: The air force of one of America’s oldest allies, Thailand, is conducting war games next week with the air force of Communist China, America’s adversary for regional power and influence.

Dubbed “Falcon Strike 2024,” the war games begin Sunday, with planes from Thailand and the People’s Republic of China taking off from the Royal Thai Air Base at Udorn in northeastern Thailand, whence American warplanes flew missions in the Vietnam War.

Hosting Chinese fighters and bombers for the 10 days of the exercises, Bangkok is expected to deploy only its Saab JAS 39 Gripen fighters and Saab 340 early-warning planes, made in Sweden, not its American-made F16s, which compete for sales to the Thai air force. The Americans were believed to have objected to exercises in which the Chinese might hone their skills against the exact same model planes that have long been a mainstay of the American Air Force.

As a relatively pro-regime newspaper in Hong Kong, the South China Morning Post, observed, “the decline” in relations between America and Thailand “has allowed China to step in, with Bangkok bolstering military ties with Beijing and making several arms deals.” China and Thailand, it said, “have broadened the scale and scope of their joint military exercises, growing from just one drill in 2017 to three last year covering air, land and sea operations.”

While Washington remained largely silent, the Chinese propaganda machine has waxed exultant in what Beijing clearly sees as the latest evidence of its growing grip over Southeast Asia. Global Times, China’s English-language propaganda sheet under the wing of People’s Daily, quotes a “Chinese military expert,” Fu Qianshao, as saying the exercises will feature “Chinese special operations forces, possibly airborne troops,” adding ground forces to the exercises in the air.

Mr. Fu was quoted as saying “special operations missions could include reconnaissance and assault on positions behind hostile defense lines, including air fields, surface-to-air missile positions and ports.” That’s in addition to “the traditional air combat part,” Mr. Fu said, including “confrontational exercises, which will enhance technical and tactical exchanges and boost mutual trust.”

Whom, though, are the Chinese and Thai thinking of fighting? The Americans, bound to Thailand in an alliance dating to, yes, 1833, enforced by the Manila pact of 1954?

By now, though, China surpasses America in sales of military equipment.

The Sino-Thai war games are taking place amid political turmoil in Thailand, where a 37-year-old who is the daughter of one ex-premier and niece of another is likely to take over. Already selected as leader of the Pheu Thai Party, Paetongtarn Shinawatra could win when the parliament votes Friday to select a successor to the man whom the country’s highest court just kicked out of office, Srettha Thavisin, for corruption.

Ms. Shinawatra’s father, Thaksin Shinawatra, served as prime minister for five years, between 2001 and 2006, when an uprising forced him into 15 years of exile. Thaksin’s sister was prime minister between 2011 and 2014, until the court expelled her too, driving her into exile.

In all the confusion of Thai politics, Thailand’s historic policy of playing one side against another, proclaiming diplomatic “neutrality,” was bound to endure. The topic has not even come up in the latest political shenanigans.

American influence in Thailand has been waning since Washington objected to the coup in 2014 that “overthrew the democratically elected government,” the South China Morning Post said, “suspending $3.5 million in military aid and downscaling joint exercises.”

The Americans still regard Thailand as their foremost ally on the Southeast Asian mainland — and have sought to fortify the alliance by words if not deeds. First there was the 2020 Joint Vision Statement for the Thai-U.S. Defense Alliance; then, in 2022, the United States-Thailand Communiqué on Strategic Alliance and Partnership. None of which has stopped the Thai navy from almost sealing a deal to buy a Chinese S26T attack submarine.

“Washington’s main concern will be about where the Chinese-made submarine will dock,” Voice of America said. VOA quoted the author of “Thailand: Shifting Ground Between the U.S and Rising China,” Benjamin Zawacki, asking whether the Chinese-made sub would  pose “a potential [for] espionage and information gathering.”