Never mind, this looks like his birth registration under the surname of Keegan:
https://civilrecords.irishgenealogy..../02494/1925018
Superintendent Registrar's District Carrick on Shannon, Registrar's District Jamestown, Counties Leitrim & Roscommon
Date and place of birth: 1888 16th Oct, Workhouse, Carrick-on-Shannon, County Leitrim
Name: Thomas
Sex: M
Name and Maiden Surname of Mother: Bridget Keegan
Informant: John McGreevy, Occupier, Union Workhouse, Carrick on Shannon
When registered: 18 Oct 1888