Gen Yutthasak said both Thai and Cambodian authorities confirmed that there was no aircraft from either country which had crashed.
He said Thai army chief Gen Prayuth Chan-ocha and Second Army Region commander Lt-Gen Thawatchai Samutsakorn reported that the debris was most likely pieces of a satellite.
He said the satellite may be one owned by a member country of the Association of Southeast Asian Nations (ASEAN) which had been decommissioned. However, the satellite did not burn up upon re-entry to earth and fell into a field.
Meanwhile, Gen Prayuth, who was visiting the Second Army Region headquarters, said an investigation was under way to identify the suspicious debris.
He said, according to the pictures, it looked similar to the sheath of a satellite or a fuel tank.
The army chief added that similar debris fell into the same area last year so that he believed the location might have been within the orbit of flying object.
Gen Prayuth confirmed, however, that the debris was not part of an aircraft that had entered Thai airspace and was shot down by the Suranaree taskforce.
Thailand observes the code of conduct when any aircraft intrudes into Thai airspace, the authorities respond with a warning, not shooting.
In a related development, deputy director Pairin Sitthiphol of the Khao Phra Viharn National Park said the incident did not affect tourism at the Thai-Cambodian border as hundreds of tourists came to enjoy the natural views as normally.