Unlike Chinese, Dai people were really lazy and didn't bother coining their own names for most places. Bengal was just Bangal or Pangal. Saraighat was just Saraighat. For country names you have, 

India and Entire West > Merng Kla
China > Merng Khe
Myanmar and rest of NE India > Merng Marn
Northern Thailand and Laos > Merng Yon 
Xishuangbanna > Merng Ri Merng Ram (depopulated land)
Dehong > Merng Khon (crowded land)
or Merng Mao (mao tribe land)
or Tau-Xong (land below salween river)

Assam > veshali or merng don son kham (land of golden mounds and fields)
Then local names, from my memory
Jorhat > Song Kat Su (twin market)
Sivasagar > Chaemun (glorious city)
Charaidoi > Chae-rer-doi (city shining on the hill)
Namrup > Namruk (six rivers)