Which tribe of Tripura is also known by the alternate name 'Riam'?

Government ethnographic records, including the Census of India's tribe-synonym lists and each state's Tribal Research and Cultural Institute publications, often document, alongside a recognised Scheduled Tribe's official name, an alternate name or self-designation used historically by the community or by its neighbours.

Tripura's Halam community is one such case: Halams call themselves 'Hre-em' or 'Hriam' (meaning 'man'), an autonym that has been recorded and anglicised as 'Riam' in administrative and press accounts — for instance, newspaper reports on a Halam land-survey protest in North Tripura describe the community as 'also called Riam'. Hence Halam is the tribe referred to in the question.

The remaining options are separately documented Scheduled Tribes of Tripura with no recorded link to the name 'Riam':

• Chaimal — a Scheduled Tribe concentrated mainly around Ambassa in Dhalai district.

• Chakma — a Scheduled Tribe with origins traced to the Chittagong Hill Tracts, settled across Tripura, Mizoram, and Arunachal Pradesh.

• Jamatia — one of Tripura's largest indigenous communities, traditionally organised under its own socio-administrative institution, the Jamatia Hoda, headed by a Hoda Okra.

So, among the offered options, Halam is the tribe of Tripura also known by the alternate name 'Riam'.