The capital of Thailand, I'm sure, is somewhere in Asia (5)
I believe the answer is:
tibet
'in asia' is the definition.
(I know that Tibet is part of Asia)
'the capital of thailand i'm sure is somewhere' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'thailand' could be 't' (abbreviation on car registration plates) and 't' is found in the answer.
'i'm' could be 'i' (I've seen this in other clues) and 'i' is located in the answer.
'is' could be 'be' and 'be' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tibet that I've seen before include "Land of the Dalai Lama" , "Chinese region" , "Nominally autonomous region of China" , "High mountainous area" , "Nepal''s neighbour" .)