The area surrounding a three-storey apartment block which partially collapsed in Muang district of Samut Sakhon on Wednesday evening has been declared a disaster zone.
Meanwhile, in Samut Prakan, the Engineering Institute of Thailand (EIT) is also investigating 20 houses in Bang Sao Thong district where pillars and ceilings were found cracked on Wednesday.
The decision on the apartment areas was taken at an urgent meeting called by deputy provincial governor, Theerapat Katchamart, which also ordered that a working panel be formed to establish the cause of the subsidence within two days.
Another committee is examining the building's design and whether it had been approved by planning specialists.
A sign has been put up declaring the area off-limits to unauthorised personnel, despite media reports the Theerapat-led meeting had ordered local officials to allow tenants to swiftly return to their apartments to retrieve essential belongings.
Now that a disaster zone has been declared, the provincial office can activate emergency funds to be disbursed as relief for those affected.
The building in Soi Seree Factory, tambon Phanthai Norasing, shook and then partially collapsed at 7pm on Wednesday, sending startled residents fleeing for safety. The incident was captured on video and went viral on social media. No casualties were reported.
Most residents were factory workers and many were in their rooms at the time, according to media reports.
CCTV camera footage showed the building suddenly subsiding in a cloud of dust and rubble. It could then be seen leaning backwards, with the first-floor pillars at the front of the building severed at the top.
The building remained standing, however, and terrified residents were all able to exit the premises unscathed, even though some had to break their way out of their rooms because doors were jammed shut or blocked. They said room walls and ceilings were all cracked.
Building owner Yiam Kamlim, 67, said it was built in 2015 and its foundation piles were 21 metres deep. Her tenants would be re-housed at a new apartment building that stood on 30-metre-deep piles, she said.
Local officials cordoned off the damaged building, which was closed to the public, pending a full investigation.
Meanwhile, Mr Theerapat said some displaced tenants were being accommodated temporarily at Ms Yiam's house.
The EIT surveyed the site yesterday with a team of experts bringing in equipment to gauge the extent of the structural damage and investigate the possible cause of the subsidence.
Institute president Thanes Veerasiri said a nearby pond may have compromised the building's structural strength.