While it does not sound like the most exciting property on earth and plainly not the best Accor property in Bangkok, the OP's statement of "avoid at all cost" seems to me over the top; too much drama and hyperbole for what sounds like, at heart, merely like a mediocre property. But then, that is not unusual for Mercure properties which are sometimes OK and sometimes not so much but, in any event, not normally the kind of upscale properties the OP seems to be expecting.