Dont know about smoking, but I flew domestic with them 5 months ago. Passenger in front noticed his seat was wet (vomit). Unsmiling stewardess gave him a blanket to sit on. He sat on it, he had no choice. He wasn't smiling either.
Anyway, if you search on pprune for Biman, you will see some postings on how they are on the brink of bankruptcy (they've been on the brink for some 16 years or so).