Health officials in Phetchaburi have ordered that six sub districts of Khao Yoi be put into 14 day lockdown.
The sub-districts are Huay Rong, Nong Chumphol Nua, Nong Chumphol, Sra Phang, Bang Khem and Khao Yoi.
A total of 14 checkpoints have been set up to prevent people from entering of leaving the affected areas without prior permission.
The move comes as the province battles a large cluster of infections at the Cal-Comp Electronics factory in Khao Yoi.
On Sunday, health officials confirmed they had discovered another cluster at a shoe factory also in Khao Yoi where 21 workers were infected.
On Saturday, 754 new COVID-19 cases were discovered, of which 745 were from factory workers.
The cumulative number of infections in Phetchaburi since April 1 now stands at 5,191 as of May 31.
The cluster at the Cal-Comp Electronics factory in Phetchaburi, as well as the two clusters found at pineapple processing factories in Hua Hin earlier this month has seen officials increase inspections at factories around Hua Hin.
Factory owners have been ordered to make sure screening of all staff is in place and two quickly report any staff members who show symptoms for COVID-19.