Welcome to Ireland Reaching Out and many thanks for your query to the message board.
Yes, there is an 1848 marriage record for John Halpin Thompson who married Maria Julia Knox also of Ballina on 7 March 1848. She was listed as a spinster whose father was Anesly Knox, a postmaster and he also appeared to be a witness to the marriage as was William Mally Junior. The ceremony was performed under the COI rites in Ardnaree.
As to further information about John Halpin Thompson, you might consider the Petty Sessions which are available through FindMyPast. Ballina may be included in those records which list all cases that came before the local courts.
In addition, newspapers in the Ballina area for that particular time period might also be useful.
There doesn't appear to be any reference of a birth or baptism for a John Halpin Thompson in County Kildare, however, you might also consider researching the COI records in Dublin (adjacent county) through the Irish genealogy website (www.irishgenealogy.ie).
As you have a date of death for him, do you have any other information about his family or parents? That would be helpful.
Good luck in your research. If you have further questions, please do not hesitate to contact us.