Army deputy spokesman Col Winthai Suwaree said that according to authorities in Yangon, 13 Myanmar soldiers were shot dead in a clash with the mystery group.
The clash was said to have taken place at Ban Inthanin Kwang in southern Myanmar's Kawthaung province, which borders the Kra Buri district of Ranong, on Thailand's Andaman Sea coast about 400 kilometres north of Phuket.
However, there was no such incident, he said. "The misunderstanding was caused by a miscommunication among the Myanmar soldiers."
According to Col Winthai, the 13 soldiers, who had been patrolling the area, lost contact with their base shortly after hearing the sound of what they thought was gunfire coming from the trees. One soldier who had lost contact with the men assumed they had been killed and reported the misinformation to the Myanmar army who then reported it to their Thai counterparts.
It was discovered later, however, that the gunfire-like noise was actually the crackling sounds of a bush fire, Col Winthai said. The missing men were later found fit and well, he said.
Foreign Minister Surapong Tovichakchaikul confirmed there had been no clashes on the Thai-Myanmar border.
It was just a misunderstanding by the Myanmar authorities, he said.
Officials from the Thai embassy in Yangon have met with Myanmar officials to resolve the matter, Mr Surapong said.