So, looking at the current playing field now,... it appears to favor the ruling party,... given the positive developments with North Korea.
Can we say they are expected to claim a comfortable win?

Well,... we won't know for sure until the votes are counted,... but final opinion polls that are allowed to be released ahead of the local elections show the ruling party in commanding lead.
New polls have been banned from being released from yesterday,... so those are the last statistics that voters will be able to see.
Out of 17 metropolitan cities or provinces,... the ruling party is in the lead in 14.
The main opposition party is leading in 2 regions,... but by a close margin,... while an independent candidate leads one area.
Now given that the ruling party aimed to win at least 9 and the opposition 6... we can say the main opposition is far behind its goal.
Same goes for the by-elections,... out of 12 districts,... the ruling party is in the lead in 11.
The main opposition party has claimed that the polls are inaccurate and not to be trusted,... but almost all polls released so far show the ruling party has a safe lead.