BANGKOK, Thailand -- Thailand's U.S.-supplied F-16 warplanes and Swedish Gripen jets bombed at least three Cambodian casinos during the past week in a gamble Bangkok hopes will obliterate its enemy's alleged ability to fire armed drones from the border zone complexes and stockpile rockets, mortars, and other weapons.

The big white-walled casinos are easy targets in the green forests and brown scrubland because Cambodia has no effective military air force to defend them.

Cambodia has not fired its anti-aircraft weapons during the war which began in July, perhaps predicting a devastating response from militarily-mightier Thailand.

Cambodia's casinos are some of the biggest and strongest-built buildings along the frontier, constructed with millions of dollars from gamblers' and investors' money.

The well-equipped casino complexes could offer Cambodia's military formidable structures, but it was not possible to independently confirm their dual use.

Cambodia mostly uses mortars and unguided, ground-to-ground, Soviet-era, truck-mounted 122mm BM-21 multiple rocket launchers, which blindly fly over the treetops into Thai territory with poor accuracy.

Cambodia's more-precise armed drones have increasingly impacted Thailand with direct hits, making drone launching sites a priority.

The U.S.-trained Thai army said on Thursday (Dec. 11) it suspects foreigners are helping Cambodia fly bomb-laden drones to hit specific targets, because Cambodia's unguided mortars and rocket launchers are inefficient.

The Second Army Area, which guards Thailand's 500-mile-long curved border with Cambodia, said Thai troops overheard Cambodian military radios use the English word "finished" when several drones dropped mortars on Thailand.

The Thai army said it tracked the voice to Thailand's Ubon Ratchathani province which borders Cambodia, but did not elaborate.

Cambodia uses "first-person view drones" to drop 82mm mortars, the Second Army said.

Cambodia also flies mortar-carrying "suicide drones" which deliberately crash into Thai military bunkers' doorways, shredding troops sheltering inside, the army said.

Each bomb-carrying Cambodian drone is supported and videoed by a nearby "target identification drone" which returns to base for analysis.

Thailand and Cambodia have also been digging trenches, unspooling barbed wire and engaging in gritty foxhole-to-foxhole clashes.

The escalating warfare is confined to narrow border zones along Thailand's northeast provinces of Surin, Buriram, Sisaket, Ubon Ratchathani, and Trat, plus Cambodian provinces on the opposite side of the frontier's forests and steep cliffs.

Since Dec. 7, scores of troops and civilians on both sides perished during the worst battles since the war began.

More than 50 people, including troops and civilians, have reportedly been killed on both sides in the five-month-long battles.

Thailand holds 18 Cambodian prisoners of war.

Thai forces said they minimalized damage while bombing three Cambodian casinos' lavish buildings because civilians may have been inside, including illegal scammers who trick foreigners out of their life savings through fake online investment and romance schemes.

For the first time during the war, Thailand's navy fired from a ship on Wednesday (Dec. 10) in the previously uninvolved Gulf of Thailand, to hit an alleged inland Cambodian casino being used as a military base near Thailand's Trat province, which is on the gulf and also borders Cambodia.

In the Gulf of Thailand's calm waters and cool tropical weather, a cluster of helmeted navy men gathered on the Thai ship's bow and fired an unidentified weapon, producing a hot, glowing, yellow-and-orange flash.

Trat province abuts Cambodia's Cardamon Mountains and is washed by the Gulf of Thailand's shallow northeast waters which are peppered with inhabited islands, navy facilities, and oil rigs.

The U.S. Seventh Fleet routinely uses the Gulf of Thailand when its aircraft carriers and other vessels dock nearby along Thailand's coast between Trat and Bangkok.

"Royal Thai Navy ship HTMS Thepa 525 opens fire in the Gulf of Thailand in support of marines striking Cambodian military targets in Nong Ree town, Muang district of Trat," said the caption of the navy's distributed photo showing the ship's weapon shooting into the sky.

Naval forces based along the gulf were chosen to lead the assault because of their proximity to what Thai media identified as Cambodia's Thmor Dar Casino which allegedly launched armed drones.

The navy said it also attacked houses along Trat province's border where Cambodian snipers allegedly stockpiled multiple-rocket launchers.

Cambodia responded with heavy artillery, the navy said.

A Gripen jet dropped high-explosives on Tuesday (Dec. 9) onto a second large Cambodian gambling venue -- the Royal Hill Resort and Casino -- in O'Smach town in Cambodia's Oddar Meanchey.

The Gripen blasted parts of the fortress-sized casino, setting fire to buildings nestled amid scrubland across the border from Thailand's Sisaket province.

F-16s on Monday (Dec. 8) destroyed a third multistory Cambodian casino which allegedly launched bomb-carrying drones into Thailand's Ubon Ratchathani province.

Thailand suspects other Cambodian casinos along their frontier were also being used to unleash weaponized drones.

Thailand and Cambodia have been blasting each other along their frontier with rockets, mortars, suicide drones, gunfire and other weapons in during several days of escalating battles, trying to strengthen their positions while bracing for a possible phone call from U.S. President Donald Trump demanding a cease fire.

Mr. Trump was expected to phone Bangkok and Phnom Penh on Thursday (Dec. 11) and possibly threaten to increase U.S. taxes on imports from the two Southeast Asian enemies unless a cease-fire is reestablished.

It was unclear why President Trump had not yet phoned as of 3 p.m. Bangkok time Friday (Dec. 12).

Scheduling may have been tricky because of a 12-hour time difference between Washington and the two warring Buddhist-majority nations.

The rising death toll and escalating warfare endangered President Trump's "joint declaration" peace agreement, signed with Thailand's Prime Minister Anutin Charnvirakul, Cambodia's Prime Minister Hun Manet, and Malaysian Prime Minister Anwar Ibrahim in October.

“I think I’m scheduled to speak to them tomorrow,” the president told White House journalists on Wednesday (Dec. 10).

"They’ve been fighting for a very long time, many, many, many decades. But I got along great with both. I found they were two great leaders, two great people, and I settled it once.

"I think I can do it pretty quickly. I think, I think I can get them to stop fighting. Who else can do that? Think of it," the president said.

Bangkok is a non-NATO treaty ally with Washington, and has strong, centuries-old links with neighboring China.

Phnom Penh is close friends with Beijing, but has opened up to Washington during recent months.

In December, Prime Minister Anutin became hawkish and said, "With what they [Cambodia] have done to us, there will not be any negotiations."

"If Prime Minister Anutin Charnvirakul refuses to negotiate a ceasefire, Thailand could be seen by the world as the aggressor," wrote political columnist Pravit Rojanaphruk.

"It could also affect Thailand’s exports to the U.S., which account for about 20 percent of Thailand’s total exports. It could even impact tourism," Mr. Pravit said.

Prime Minister Anutin dissolved parliament on Thursday (Dec. 11) to allow fresh elections, apparently hoping his wartime performance will return him to power.

As required, the Royal Gazette published a decree endorsing Mr. Anutin's dissolution of the House of Representatives, allowing a nationwide election within 60 days.

The worsening border war meanwhile was also becoming personal.

"Cambodia’s long-range weapons were previously positioned to protect Hun Sen in Phnom Penh," Thai Army National Defense Studies Institute adviser Lt. Gen. Wanchana Sawasdee said in a harsh warning to Cambodia's de facto leader Senate President Hun Sen.

"If credible intelligence indicates that such weapons present an imminent threat, we will destroy them," Lt. Gen. Wanchana posted on Facebook on Thursday (Dec. 11) in a chilling "Message to Hun Sen."

"Because Hun Sen prioritizes his own safety above all else, he has no choice but to move those long-range weapons farther away from himself.

"Cambodian military bases are embedded within civilian homes and buildings, using them as firing positions and weapons-control centers, effectively using civilians as human shields.

"If an imminent threat is positioned at anyone’s house, that threat will be neutralized regardless of where it is located," Lt. Gen. Wanchana said.

Mr. Hun Sen, earlier wrote online: "Cambodia wants peace, but Cambodia is forced to fight back to defend its territory."

Thailand's powerful Internal Security Operations Command (ISOC) -- established in 1965 during the Cold War with the U.S. Central Intelligence Agency to suppress communism and other political and military threats -- urged Thais to report any people suspected of being "Cambodian spies."

"These include foreigners acting secretively or avoiding identification, photographing or recording information in restricted areas, entering restricted areas without reason, or engaging in unusual contact or movement near government or security areas," ISOC said.

Before the war, Cambodia's casinos were popular with local and foreign gamblers, including passengers arriving and departing on shuttle buses to and from Thailand.

Some casinos were allegedly also being used mostly by Chinese scam bosses who enjoy virtual immunity in Cambodia because of the Southeast Asian nation's lax law enforcement and corruption, investigators said.

Those casinos allegedly included heavily guarded compounds where online scammers contacted unsuspecting people worldwide to drain their bank accounts, resulting in billions of dollars in stolen cash and cryptocurrency each year.

Many of the foreign, mostly English-speaking scammers have been tricked, kidnapped and tortured into working in the scam centers while others eagerly accept the relatively high wages and other benefits from their illegal  work, investigators said.

Some of the biggest scam operators have been named by U.S. officials for alleged money laundering and other crimes in Cambodia and Myanmar, but it was unclear if their network included the three bombed casinos.

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Richard S. Ehrlich is a Bangkok-based American foreign correspondent reporting from Asia since 1978, and winner of Columbia University's Foreign Correspondents' Award. 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