Straight married guy here. I've always worn more bikini type underwear, nothing exotic, just your average 5 pack Jockeys you can find at Walmart. I always wanted to try out a thong, but didn't really have the guts.
Recently when packing for a trip my wife realized I only had like 5 pairs of underwear. That wasn't going to cut it for an 8 day trip (not about to do laundry on vacation). She helpfully went to the store to buy me some more underwear. Unfortunately, she bought some of the largest briefs that could be sold. Not kidding I think they went up to my belly button.
Those were okay for the trip, and for a couple of months after, but eventually I had enough. I needed new underwear. My plan was to simply find old fashion Jockeys on Amazon and order them up. Little did I know while browsing all the different options available! My wife happened to "catch" my browsing when I pointed out a MuscleMate Thong. I said, "I could try out one of these too" and she was sheepishly up for it. Even picked out the first color (yellow ;-) When they finally arrived (thanks Amazon Prime) I put them on right away. We had a few things to do that day, but in the evening she gave my backside a little pat and realized what I had been wearing. She wanted to check them out, and lets just say it led to a little fun.
I call those my gateway thong, since since then I've bought a three pack of some IKingsky thongs, 5 pack Braziians backs and er, joined a thong forum!
I'm trying to slow down my purchasing for now, I don't want to overwhelm the poor wife. She's adjusting to my "coming out" as much as I am. Either way, 2019 is a banner year for me.