Do you have the location GPS for the legendary Nakorn Nowhere ?
Checking Chevron Thailand's website found
this PDF with a useful map on the second page including the oil/gas fields and three towns including Nakhon Si Thammarat (note, another different spelling). No GPS, but Wikipedia has
a page for the airport here and one of the links there goes to World Aero Data site
here, which says
Latitude 8.539617
08° 32' 22.62" N
Longitude 99.944725
099° 56' 41.01" E
This does of course assume they operate from that airport and not a dedicated heliport!