I think Todd will confirm but you don't have to do a 90 day report with a multi O only leave and come back...good wishes for your up coming wedding :-)
Best of luck Paul there's a cheap hotel we have stayed in 5 minutes up the same road as the Embassy called the Moonite Boutique Hotel about 600 baht a night with a small car park at the rear :-)
No a she had a UK visa there is an agreement between UK and Ireland that enables the same visa to be used for certain nationalities...Thailand is one of the nationalities :-)