Just days after the killing of a prominent Cambodian government critic last year during a crackdown by the country's longtime leader, President Barack Obama dispatched Washington's chief human rights envoy to Phnom Penh to attend the activist's funeral.

In meetings with Cambodian authorities, then-Assistant Secretary of State Tom Malinowski warned the military not to intervene in the political turmoil or else crucial U.S. ties would suffer, sending a clear message that America stood behind the opposition.

It was one example of the kind of high-level, rapid-response U.S. diplomacy that President Donald Trump has so far avoided in Cambodia even as the Southeast Asian nation — together with many of its neighbors — has lurched increasingly away from the democratic path.