looking for answer to this problem.

my friend's 2 children ages 5 and 6 are dual nationality thai and british.

they have passports for both countries.

they came to Thailand last week on their thai passports which had already expired.but were stamped through and told to renew their passports but are having a hard time doing this ,due to issues with their names not included in the house book.

so my question is can they leave Thailand on their uk passport?

thank you