Whilst I've had a multitude of Tourist Visas over the years I've never stayed longer than 60 days.

Not having first hand experience of Non Immigrant visas how exactly do they work, and what advantages to they have over tourist visas. I would imagine I would be staying for approx 10 weeks with multiple trips ?

Am married to a Thai aged 51.

Whilst I appreciate I can "search" this I would appreciate first hand information.Cardiff Consulate are very sketchy with their information via emails.

Have no knowledge of that Consulate but it would appears you could qualify for non immigrant O visa on basis of Thai wife (with marriage certificate) or intent to retire (age over 50 with perhaps some proof of funds).

Such visas are issued single entry for a 90 day stay and multi entry for one year of unlimited number of up to 90 day stays.

The advantage of a multi entry is you get 90 days on any entry and only have to exit/return for a new 90 day stay. They can also be extended for one year at Immigration by meeting the specific requirements (40k per month or 400k in bank two months for marriage or 65k per month or 800k in bank two months or a combination to meet 800k for retirement).

Have no knowledge of that Consulate but it would appears you could qualify for non immigrant O visa on basis of Thai wife (with marriage certificate) or intent to retire (age over 50 with perhaps some proof of funds).

Such visas are issued single entry for a 90 day stay and multi entry for one year of unlimited number of up to 90 day stays.

The advantage of a multi entry is you get 90 days on any entry and only have to exit/return for a new 90 day stay. They can also be extended for one year at Immigration by meeting the specific requirements (40k per month or 400k in bank two months for marriage or 65k per month or 800k in bank two months or a combination to meet 800k for retirement).

No I don't intend to retire.

I have certified English Copy of marriage certificate here in the UK so that alone should enable a multi entry visa to be granted ??

Is this the visa whereby if you enter Thailand for example just a few days prior to the expiry of the one year, than you still get 90 additional days ?

^^^Yes and Yes.