Thais have filed a complaint against Cambodian leaders over alleged war crimes during the current border clashes.

The royalists marched to the Crime Suppression Division in Bangkok to lodge the complaint against former Cambodian premier Hun Sen, sitting prime minister Hun Manet, and Defence Ministry spokesman Maly Socheata, on December 19

Led by Rachen Trakulwiang, president of the Federation of Thai Defenders of the Monarchy, the group decried the trio's alleged war crimes, vowing to pursue 'maximum legal action' against them.

He accused former Khmer Rouge henchman Hun Sen of 'repeatedly breaking promises' made during talks and allegedly painting Thailand as the aggressor in the conflict.

He also urged Interpol to issue red notices for the three, labelling them as 'war criminals' despite having diplomatic immunity.

Rachen said: 'Thailand must seize this opportunity to deal decisively with Cambodia in every dimension. Otherwise, Thailand will miss the chance and lose the advantage.

‘Thailand should not be viewed as a 'big brother' bullying a 'little brother' because Cambodia will become a constant thorn in our side.'

He added that prosecution was 'another way for Cambodia to lose'.

The group also filed further complaints against Cambodian nationals allegedly stirring unrest in Thailand.

The suspects were accused of hurling homemade bombs, taunting locals, tearing up Thai banknotes and trampling on the national flag.

Territorial conflict 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 21 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 commander Hun Sen 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.