Yes , this class were prolific and never forget seeing one anchored in H.K., and saying to a mate , 'blimey is she lost or something'? This was at the height of the Vietnam War so presume she'd delivered something to North Vietnam that went Whizz, or Bang or splut.
The example seen in Hong Kong had not delivered military equipment to North Vietnam. In the late 1970s, at least one of the class, the Poel, was transferred to the ownership of the Government of the Socialist Republic of Vietnam in a show of solidarity with another communist government. She was renamed Song Ba and transferred to that country's flag. She sailed regularly from Hong Kong to Haiphong.
already in 1960 two of these 840-class coasters were given as solidarity presents to Vietnam, the ALGENIB and SCHEDIR, both built 1958 by Peene-Werft as all the others. They were renamed DOAN KET and THON NHUIT respectively.
POEL spent from 1965 a few years in the cross trade between Abidjan and Spanish-Guinea. 1976 she left her Rostock home for Singapore as a feeder between SGP and Vietnam. A few month later she was trading cement between Haiphong and Vinh. 1979 she was decommissioned and presented to the Technical Shipping School of Haiphong, renamed as you said in SONG BA.