The seven workers tested positive for both the Alpha and the Delta variants of the virus, according to the Public Health Ministry at a Monday briefing.
Tests at their construction camp on 1,737 workers confirmed 1,327 infections – almost three-quarters (73.7 per cent) with Delta and the rest with the Alpha variant.
The ministry is concerned that cases of mixed infection could eventually spawn a new coronavirus variant.
It reported that Delta is now the dominant strain in Bangkok, accounting for 57.1 per cent of new infections.