I know many, many people who have been. Some regularly, some for one off longer travelling.
Thailand is more "commercial" ie, geared up towards travellers (ever seen The Beach?!). You can have lots and lots of fun, but I think it will feel more resort like in lots of places. Lots of young travellers out to have a good time party. I think a great time could be had though, I'd like to go once!
If you want more authentic travelling then I'd probably go for some of the Indonesian or Malaysian Islands. Personally!! I did a lot of reading up on Indonesia as I wanted to go.... Looks amazing, and definitely going to get a real experience (and you can visit orphaned orangutans!)
As for the military coup stuff, you can pretty much get that in all of those countries. My friend is in Thailand right this very second, and it is fine. She has posted about it on her Facebook and I don't think it's particularly worrisome. She's having a great time
Always. Always. Check before you fly. To any country!!!!!!!!!!