The negative assessment on Yoon's conduct of state affairs gained 1.1 percentage points to 64.5 percent, according to local pollster Realmeter.
Support for the ruling conservative People Power Party dipped 1.3 percentage points over the week to 38.4 percent last week.
The main liberal opposition Democratic Party's approval rating rose 1.4 percentage points to 46.0 percent.
The minor progressive Justice Party won 3.8 percent of support score last week, up 0.5 percentage point from the prior week.
The results were based on a survey of 2,519 voters conducted from last Monday to Friday. It had plus and minus 2.0 percentage points in margin of error with a 95 percent confidence level.
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