I've just spoken to a chap at the consulate in Cardiff.
My Son and Partner (we're not married) are currently in Thailand and I'm at home working. I rang to see what my options were re: multiple entry visas.
I thought I was going to be told that because we aren't married I'd have to have a Triple entry tourist visa, however I was told that if my Mrs. writes to me inviting me to visit her and my son with a copy of the boys birth certificate I can get a 12 month Non Immigrant O visa.
I'd never heard of this before and it was a nice surprise. I might just be going over old ground i didn't search the forum, but if it helps anyone else then happy days.
Al