Update - For anyone in a similar situation. Nigerian Nationals living in UK with a resident permit - Thai Embassy will accept UK police clearance. This can be obtained from the website below:

https://www.acro.police.uk/Police_Certificates_Online.aspx

The embassy will not accept CRB/DBS.

Hi there,

My husband went to the Thai embassy to submit his application for a Thai visa today for our upcoming trip to Thailand in December. Unfortunately, a voice mail has been left on his mobile to say that they are unable to process his visa as he is missing this notorious NDLEA clearance certificate - and he must obtain the certificate and go to the Thai Embassy in Abuja??! We were of the impression that he would not need this certificate as he has a UK resident permit and has not lived in Nigeria for many years.

We have booked and confirmed all of our travel and hotel arrangements and unable to change or cancel. Please can anyone offer any advice particularly KOKOLOU and FALIYU1 who both seem to have been through this jarring and frustrating experience.

Thanks.