Military command units from both sides promptly contacted each other to find out what happened.
It was later confirmed the explosion was caused by junk metal from a fallen satellite, not an artillery shell.
The Suranaree Task Force, which is overseeing the border, reported a blast in the sky and smoke above the ground to the north of tambon Sao Thong Chai, Kantharalak district, Si Sa Ket province.
That area was a battle zone between Thai and Cambodian troops in early 2011.
Authorities investigated and found metal shards in the area which were identified as parts of an old satellite that had fallen to Earth. No injuries were reported.