He was 82.
The cremation will be held in Doon at 11.00 AM tomorrow, his family memebrs said.
Lajja Ram was elected to Himachal Assembly from Doon in 1990 as a Janata Dal candidate and later joined the Congress and retained the seat in 1993, 1998 and 2003.
His son Ram Kumar is a sitting MLA from Solan district's Doon constituency.
Governor Acharya Devvrat and Chief Minister Virbhadra Singh have expressed grief over his demise.
The CM, in his condolence message, said that Chaudhary Lajja Ram was a popular mass leader of the area and his contributions for the development of Doon area were immense.