Does he have the ability to work at all? If so, he could move to Northern Ireland (UK) and exercise his treaty rights (by being an EEA citizen moving to another EEA country) by working part time. To get the visa for the UK, his wife would need to apply for an EEA family permit from the British Embassy in Thailand (or it may go through the British Embassy in KL, Malaysia if I remember correctly). Then she could travel to the UK to be with him. After a period of working in the UK (or another EEA state), they could then move back to ROI and his wife could apply on EU1 form for residence. Whilst it's not necessary to be married for this to work, it would probably help as if you're not married you have to produce evidence of a durable relationship.
This above is called the Surinder Singh route. Most of the evidence and discussion so far is about British people traveling to Ireland (or other EEA countries) to exercise treaty rights and then returning to the UK. However, it does work the other way around.
The Irish authorities now have financial requirements which are listed in this document:
http://www.embassyofireland.cn/visa.php?eid=32. There are issues for people on benefits: "An Irish citizen, in order to sponsor an immediate family member, must not have been totally or predominantly reliant on benefits from the Irish State for a continuous period in excess of 2 years immediately prior to the application". I don't think it will be easy for him to get her back on a spouse visa if he is solely dependent on benefits.
Also, bringing her in on a tourist visa and then trying to regularize her residence would be a really long process. He should become familiar with the info on this page:
http://www.inis.gov.ie/en/INIS/Pages/WP07000024.
I'm not sure that there is a really easy way around this (if he's not able to work in another EEA country).
RE Getting married: If it's easy in Thailand then I'd say get married in Thailand. It would probably be easier for him to get the required visas/permits (if there are any) for Thailand than for his future wife to get them for Ireland.
PS: I've made references to 'wife' throughout this post - it should be fiancee.