The frequency and degree of aftershocks from the May 5 quake had declined sharply, and people whose houses were intact could return home, NDWC director Suebsak Khaosuwan said on Saturday.
He also advised those whose houses were affected to have experts guarantee the safety of their residences first.
On Saturday morning a 200-metre section of Highway 118 was found to have subsided by about two metres. Highway workers created a detour around the site in Ban Huai San village of Dong Mada sub-district of Mae Lao district in Chiang Rai.
Soil liquefaction and the appearance of underground springs were reported in Mae Lao, Phan, Pa Daet and Mae Suai districts of Chiang Rai on Friday. Authorities said such phenomena were normal after an earthquake.
The earthquake measuring 6.3 on the Richter scale occurred about 6pm last Monday and was considered the biggest ever to have struck Thailand. Its centre was in Phan district of Chiang Rai province.
While property damage was extensive, there was only one fatality, an 83-year-old woman who was killed when a wall in her house collapsed.
Building damage was reported in Chiang Rai, Chiang Mai, Lamphun, Lampang, Kamphaeng Phet, Nan, Phayao and Phrae. Affected were 16 archaeological sites including temples, 73 schools and about 8,000 houses. Chiang Rai was the hardest hit.
About 540 aftershocks were reported after the quake.