Just to verify if I get it correctly.
Looking at the outlet's diagram:
Local L --> Line1
Local N --> Line2
Local Earth -->Nearby earth rod
Does it mean that I can get something like this, cut the existing plug off and connect the L14-30 male plug instead, wired as per your instructions?
It will be a kind of a stationary setup, since it needs to be attached to the Earth rod.
https://www.lazada.co.th/products/amc-4-3-30-2-i2837402191-s10353318778.html?clickTrackInfo=undefined&search=1&spm=a2o4m.searchlist.list.i40.54304abfAAZTj3
Regarding to your point on "(it doesn't actually matter)"
Did you mean that the Local L and N could be connected to either Line1 or Line2, interchangeably, as it doesn't actually matter?