If it is the Beach in Pusan, nice. Usually spelled with a W before the oon or
Haeundae Beach.
Not a thai beach. Urban. About the best Urban Beach area of S. Korea. I used to go there often. Pusan aka Busan is a nice city. Has 2 subway routes. About 3-4 million people. I lived in the hills about 15k from this beach. Has a Sheraton Hotel on the Beach. Losts of Sea Food Restuaunts but much more expensive than Thailand. Pusan itself is nice. There is a very interesting Downtown pedestrian walk area. Not a lot of expats in PUSAN. Mostly teachers, Sailors, professors. I enjoyed it. For cities I feel Pusan is the Best in SK. There are some nice Buddists cites on the hills. There is a nice hot springs. The bullet train is quick and runs to the city center.

Good luck

It ain't Thailand.
As housing in Pusan is very expensive make sure you have a suitable housing situation before signing on the dotted line.