Google for 'worst hotel in Thailand': step forward the Royal Parkview Hotel Bangkok!
https://www.tripadvi...el-Bangkok.html
But Google for 'worst hotel in Bangkok': hello Ambassador Hotel!
https://www.tripadvi...ok-Bangkok.html
I stayed at the former once, and it was probably shit (can't remember, but the word 'once' might well be a clue). Never stayed at the latter so can't comment.
jack