The German, who set a new track record alongside new brakeman Alexander Schüller on Saturday, sled to victory once again despite not liking the track.
The PyeongChang champion finished in 1:40.25 with brakeman Martin Grothkopp, just six hundredths of a second ahead of the Latvians (1:40.31) as Oskars Kibermanis and Matiss Miknis were forced to settle for second place.
In addition, World Cup debutant and fellow German, Christoph Hafer, together with Tobias Schneider, placed third finishing in 1:40.50.
Friedrich reigns supreme again with four-man bobsleigh victory
"We did not really like this track, it was rumbling and rocking, but we got in," said Friedrich after his second victory in the tricky ice near the capital Riga.
"We were reasonably good at the start, even though we did, our sledge pulls on the last metres of the track again properly."
Britons Hall and Cackett claim fourth as Friedrich and Schueller take two-man top spot in La Plagne
Lochner storms to European four-man title