Considering that South Korea receives most of their energy from the Middle East it seems like it would be in their interests to ensure the Strait of Hormuz remains open:

South Korea is closely monitoring the situation in waters off Iran, including the U.S.’ possible request for its troops dispatch to the region, the defense ministry said Monday.
The United States has been asking its allies to join a military coalition to ensure freedom of navigation in the Strait of Hormuz amid heightened tensions between Washington and Tehran.
“So far, we have not received any official requests from the U.S. side over the possible dispatch of our troops,” Col. Roh Jae-cheon, the deputy ministry spokesman, told a regular briefing.
“South Korea is keeping a close tab on the situation in the Strait of Hormuz while opening various possibilities in consideration of potential impacts the matter could have on our side,” he added.
Another official said that the ministry “is reviewing diverse options and measures with regards to the issue.”
Some observers have said that U.S. National Security Adviser John Bolton could make such a request during his two-day visit here that begins Tuesday.
Yonhap
You can read more at the link, but so far Iran has not messed with energy shipments to South Korea. South Korea has actually had good relations with Iran to include the prior President conducting a state visit.
President Moon might calculate that dispatching a naval presence to the Strait of the Hormuz could anger Iran. Another factor to consider is the ROK may not want to cooperate with the Japanese Navy if it participates in such a maritime mission as well. It will be interesting to see what President Moon decides if asked by the U.S. to participate in the mission.







