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I believe these were Baya weavers (P. philippinus), and of three weaver species recorded in Bangladesh and the most common species around... but it's difficult to be sure, as all were non-breeding, and probably juvenile birds.
In urban setting of Cox's Bazar, very close to the beach and some peri-urban vegetable farms.
I was not impressed by birding checklist available for Bangladesh (except one found on Avibase, at https://avibase.bsc-eoc.org ), but at least all of them agreed on one point - there are three weaver species recorded in Bangladesh, Baya (P. philippinus); Bengali (P. benghalensis) and Streaked (P. manyar) weavers.