Kamatha is a Kamboja king mentioned in the Mahābhārata as one of the principal Kshatriyas taking part in the battle.
Sabhaparva section of Mahabharata refers to a king of the Kambojas called Kamatha Kamboja (कामथ). He is the second prince of the Kambojas referenced in the great epic.
After the colonization of Khandavaprastha by the Pandavas, a magnificent palace was raised by Danava Maya, for the Pandava king Yudhishtra.
To celebtrate the occasion, Yudhishtra had sent invitations to all the principal Kshatriya princes, royal Achariyas and other salient personages of the time to grace the inauguration of the imperial palace.
In the list of salient royal Kshatriya (Kshatriya.shrestha) princes so referenced, is a reference to one: Kaamboja.rajah.Kamatha i.e Kamatha, the prince of the Kambojas.
— (MBH 2.4.20-22)
Kamboja King Kamatha is mentioned along with King Kakshasena, king Kshemaka, king Kampana who terrorized the Yavanas and the king of the Madrakas. All of them are described as saliant Kshatriyas (Kshatriya shreshtha ) and had come to attend the event of Pandava king Yudhisthira’s entry to his new palace at Indraprastha. This king ‘Kamath Kamboj’ was contemporary of Yudhistra, and he graced Yudhishtra court during the inaugration ceremony of ‘Indraprastha city’ raised by Pandavas in Khandava-bana. (Ancient Kamboja, People & the Country, 1981, Dr J. L. kamboj, p 52)
It is believable that king Kamath Kamboj was the king of KASHMIR. with whom, Mahabali ‘Karana’ had to fight at Rajapura or Rajaori.
However, no further information on this prince is found at any place in the Mahabharata after this reference.
See the site below which also identifies this Kamboja King ‘KAMATH’ KAMBOJ:
“Kamat: a king of Kamboj and member of the court of Yudhisthira”