Singh, who is a relative of RJD leader and former Union minister Raghuvansh Prasad Singh, joined the saffron party in the presence of local BJP leaders here.
The former CRPF IG said he had decided to join the BJP as he was distressed over the prevailing political scenario in the country.
He said it was his cherished desire to see Modi as Prime Minister of the country.
"Modi is the only politician who can take the country on the right path as he has shown in Gujarat," the retired CRPF officer said.