The Punjabi singer passed away in hospital on May 22 in Houston, Texas, where he was receiving treatment for a brain tumour.
The song, entitled 'Yaadan' (Memories), has been written by Kuly's father Harjog Singh, who also recorded one verse of the song.
The rest of the track is performed by Kuly's brothers Surj and Manj. The music and production of the track was composed by Kuly last year.
Speaking about the recording, Manj said: "This song was the hardest one we have ever had to sing, and was very emotional for us all. Dad would tear at every line he would sing. This song is from the heart and we hope the world appreciates it."
In a further tribute to the internationally acclaimed producer, urban Bhangra singer Nindy Kaur will release a track featuring Kuly's vocals and a hook line produced for her by Kuly before he passed away.
'Yaadan' can be downloaded for free from RDB's Facebook page.
As a lasting legacy to Kuly, his family and friends have set up a 'Just Giving' Memorial Page, where donations can be made to Brain Tumour UK, which works to fund research and raise awareness of brain cancer.
Listen to RDB's 'Yaadan' in memory of Kuly Ral below: