Thailand was set for an earlier than expected election after its king endorsed Prime Minister Anutin Charnvirakul's bid to dissolve parliament on Friday, as a border conflict with Cambodia raged and the government moved to head off a no-confidence vote.

Cambodia's government accused the Thai military of attacking civilian targets, an accusation Thailand has denied.

Anutin, after speaking with Trump but before the U.S. president's social media posting, said he reiterated to Trump that Thailand’s position was to keep fighting until Cambodia no longer poses a threa...