The deadly conflict on the Thai-Cambodian border pits a longtime United States ally with decades of experience against a relatively young armed force with close ties to China.

"The U.S. already flunked the test and that should be a wakeup call," a former senior U.S. State Department official told Newsweek.

Of course, trouble at the 508-mile (817 km) shared border is nothing new. For over a century, Thailand and Cambodia have contested sovereignty at various undemarcated points in the thick jungle punctuated with culturally-significant temples albeit with scant strategic or economic value.

China has dismissed allegations that it was supplying weapons to Cambodia amid its ongoing border conflict with Thailand that has led to at least 33 people dying and hundreds of thousands displaced.

Six-year-old Sunisa Chanprakhon was looking forward to running in her school sports day in their Thai border village on Thursday when explosions shattered the morning calm.