The 6.3-magnitude earthquake that hit Phan district is considered one of the strongest ever recorded in Thailand.
Heavy construction machinery was moved in to repair Highway 118 Chiang Rai-Chiang Mai in Mae Lao district which was badly cracked and has subsided.
It was expected that the work would complete and the road could be opened by tomorrow.
The Meteorological Department of Thailand's Seismological Bureau reported that as of 4am of May 7 there were nearly 300 recorded aftershocks that rattled Chiang Rai, some as strong as 5.9 on the Richter scale.
The National Disaster Warning Centre has warned the residents in the quake hit areas particularly in Chiang Rai, Chiang Mai, Phayao, Nan, Phrae and Lampang to be aware of danger that may caused from aftershock that could continue for a period of time.
The centre earlier advised residents to stay in safe places or shelters provided by authorities for 3-6 hours, but aftershocks have continued for a longer time.