Wisanu Subsompon, deputy governor of Bangkok, told a press conference on Tuesday the damage may have been caused by an unbalanced crane.
“Work will be suspended until they have a safety plan,” he said.
The roadwork is part of a project to build elevated highways in an attempt to ease the city’s notoriously congested traffic.
Construction safety standards are lax in Thailand, where accidents are commonplace.
In 2016, at least 13 people were killed when a building under construction collapsed.
The accident had sparked protests from trade unions, who denounced the inadequacy of safety standards and the meagre wages paid to workers on construction sites.