Raja, a four-time MLA, breathed his last at his home in Nabha city in the district, family members said.
He is survived by his wife, a son and a daughter.
Singh, who was elected MLA in 1967, 1969, 1985 and 1997, was Public Health minister in the Parkash Singh Badal government in 1997.
Chief Minister Parkash Singh Badal expressed his grief and sorrow over the demise of Raja.
In a condolence message, he described him as a seasoned politician and disciplined solider of the party with qualities of head and heart.
