Thai soldiers hoisted the flag as they seized disputed land on the border with Cambodia.

Footage shows soldiers singing the national anthem at the Chong An Ma pass in Ubon Ratchathani province on December 16.

The Thai army also flew a drone carrying the flag over the conflict zone after seizing control of Hills 677 and 500, both strategic points overlooking the border pass.

Territorial clashes flared up earlier this year before a brief ceasefire, but started again this month when Cambodian troops are said to have fired on a Thai engineering team building an access road in a disputed border area.

In the most recent battles, at least 19 Thai soldiers and one civilian have been killed. In Cambodia, the number of military fatalities is believed to be much higher, though regime chiefs have not revealed the actual figure.

Around 600,000 people have been displaced on both sides of the border.

Cambodia's assault has largely been wayward, unguided rockets fired indiscriminately into Thai territory, including an attack on July 24 that killed eight people and injured 13 others. Thailand has used precision drone strikes and fighter jet strikes on military sites.

Former Khmer Rouge henchman and Cambodian dictator Hun Sen - who was a leading figure in the genocide of his own people in the 1970s before assuming power in 1985 and overseeing the murder of thousands of opposition figures and critics - has repeatedly claimed that he wants peace and that Thailand is the aggressor.

Thai officials claim the ongoing border confrontations are a threat to national security, and the areas must be secured.