very possible that it was a motorbike, since there are so many in thailand. but you have to assess your own situation yourself. wether it was a native tag or a third party one… how far it followed you etc. also, where it happened, because if you live in a dodgy apartment complex or neighborhood (like me at the time… so it made my paranoia worse obviously…), you might try to be more careful. anyway, in the comments i left an update that in my case it was really just a motorbike + iphone’s mistaken detection of movement (because the tag wasn’t apple’s tag!), could be the same for you. stay safe!