Heavy D was planning a huge comeback just before his death -- and those plans included a new music video.

Carl Thomas, who sang on Heavy D's latest album, tells TMZ that, he was in touch with Heavy two weeks ago ... and Heavy told him he was weeks away from shooting a music video for their song, "Still Missing You." Thomas said Heavy had a director in place and had picked a location for the shoot.

Sources close to Heavy D say it was all part of the singer's comeback plan. He released his new album on September 27 because it coincided with the BET Music Awards ... and he was hoping the performance would put him back on the map.

Heavy D passed away on Tuesday after collapsing outside his Beverly Hills home. He was 44.

I wonder what happened to the Boyz? Ain't no show without Heavy D!

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