Bangkok folk assembled initially in this (5)
I believe the answer is:
thais
'bangkok folk' is the definition.
Although both the answer and 'folk' are nouns, they are not in the same form of the noun.
'assembled initially in this' is the wordplay.
'initially' says to take the initial letters.
'in' means one lot of letters goes inside another.
The initial letter of 'assembled' is 'a'.
'a' inserted within 'this' is 'THAIS'.
Can you help me to learn more?
(Other definitions for thais that I've seen before include "Siamese people" , "orientals" , "Natives of former Siam" , "Asians" , "Opera" .)