1. What does it mean?
As Korean slang, 방콕 evokes 방에 콕 박혀 있다: staying firmly tucked inside your room. It is a playful way to say you are not going out, and sounds the same as the Korean name for Bangkok.
Also written or said as bangkok
2. The nuance
Travel context may mean the actual Thai capital. 방콕하다 in a casual weekend plan usually means staying in, not traveling to Thailand.
3. Examples
“비 오는 주말이라 방콕하면서 쉬었어.”
It was a rainy weekend, so I stayed in and rested.
“여행 말고 이번 휴가는 방콕이야.”
No trip this time; my vacation will be spent at home.
Sources
Sinjoeo Korean Slang Dictionary
References support the meaning and usage. Example sentences are written for NoCapWiki.