U need to miss ireland out .. get the UK visa and transfer thru london … UK visa is no good in dublin unless travelling from UK on the short stay waiver program
Going to be a challenge getting your Mrs a 6 month visa . She needs to prove there is intent to return to thailand and a reason . Ie a job
Applying for leave to enter which is path to permanent move would alternative but very expensive and not at all easy .. i assume she has not travelled much . Immigration want to see a busy passport .. an agent may be able to secure visa but not easy