My wife, her friend as she has helped do our washing. Probably a few others.
As for if anyone sees am not to fussed. I wear them for comfort as well as jockstraps. I do have boring pants for wearing in bed it helps hide the issue in the morning and avoiding the convo with my young son.
Iāve only recently started wearing them but only been brave enough to wear them under my clothes around the house, the only person that knows is my OH but she hates them so I kinda keep it secret from her too
I donāt understand the point of the question, to be honest. A thong is just a species of underwear. Big deal! As for who might know, Iām not in the habit of going round telling randoms what style of underwear Iām wearing. 
I think itās because itās not considered normal so itās something you wouldnāt want everyone to know about, obviously people know you wear underwear and usually you wouldnāt care if itās just ānormalā underwear but you might be embarrassed because itās different. Like the āhow many people know about your other sideā thread, ya donāt go round telling everyone about what you get up to in the bedroom, everyone does it, but you wouldnāt want them to know youāve got a massive stash of sex toys
Gosh - I honestly had no idea that wearing thong briefs was regarded as being anything out of the ordinary! We live and learnā¦ 
Anyone walking behind me when Iām out in the McQueen bumster jeans
Answering for my hubby but he says his mum knew as he wore thongs before we moved in together. My mother has seen when Iāve been doing washing and Iāve talked about it with my closest friend as she had mentioned about her husband wearing them.
Heās said that probably some people have seen in the gym changing rooms but nobody has said anything.
no one at work today did
and I spent the afternoon sitting next to the general manager
My ex girlfriend (she even bought some for me), my doctor, the nurse, and now the girl in the lingerie store who asked if they were for me or someone else. 
I will be that brave one day! 
My wife knows obviously and Iām sure her mum does as she does or cleaning and washing. Not sure if she has talked about things like this with her girlfriends but maybe.
the shop assistant I buy them from
I think my mother inlaw had an idea i wear thongs,
but current on holiday with the inlaws just now and she took apon herself to do a load of washing to save as much for us when we go home.
If she didnt know before she wil have worked it out by now 
Everybody who reads āWhat undies are you wearing today?ā
And my doctor, and the nurse, and the websites I buy from, and the girl in the lingerie shop, and my ex, hardly the best kept secret!
My wife and probably both our children (as one hangs the washing out on the line, the other gets it in). Its one of those weird things, I donāt advertise what I am wearing and would prefer not to be caught as such (work with tradesmen who would find it amusing, until the next thing happened anyway), but equally, so what if someone found out.
Quite a few when I think about it but only my wife knows that I wear them on a daily basis. Pretty sure my mother-in-law and wifeās best friend also know but theyāve never brought it up. Other than that, we once went to a halloween/Rocky Horror fancy dress and I purposely had my thong straps showing which did spark some comments. I suppose they will have thought it was ājust part of the costumeā.
Not sure how Iād react if people saw at work. Iām very conscious about it showing so always have a belt on my suit trousers. Then I think āI keep myself in shape, there should be no big deal about it in 2021 plus half the women in the office will be wearing thongs!ā
Iām going to get a thong for my husband in my next order. I was thinking about maybe this one or this one. Have any of you tried them? Itāll be his first thong, and heās apprehensive because he thinks a thong will be uncomfortableā¦ Do any of you have a recommendation for a comfy first one?
I have the LHM one and I find it comfortable.
If I was to wear a thong it would have to be a ladies thong I just find more sexy and nicer against my skin