Upper-class person from Thailand no longer available (4)
I believe the answer is:
toff
'upper-class person' is the definition.
(I've seen this before)
'thailand no longer available' is the wordplay.
'thailand' becomes 'T' (abbreviation on car registration plates).
'no longer available' becomes 'off' (I've seen this before).
't'+'off'='TOFF'
'from' acts as a link.
(Other definitions for toff that I've seen before include "Person of the upper classes" , "Aristo" , "Dandy" , "Posh geezer" , "Rich or upper-class person" .)