I believe that IF YOU ARE LUCKY you might get away with being 1 day overstay at the airport, on the way out of the country. You will certainly get fined for being 2 days over, although I am uncertain what the daily fines are now.
Without wishing to sound 'preachy' I have always avoided overstaying a visa like the plague.
I know that a great many people are unconcerned about it & the penalties inflicted are normally pretty minor. However, if you were caught by officials on a bad day they have pretty draconian laws behind them if they ever decide to make an example of someone. So I try not to give them that chance.
up2you wrote:Sorry to bother you, but another question... Does it cost about $30 for each person visiting Laos, for myself and my Thai wife also? And who collects the money, Thailand, Laos, both?
If your wife is traveling on a Thai passport then she does not have to apply for (& so pay) for the entrance visa to Laos.
I believe that it is free to enter for all ASEAN passport holders. The cost (hence my vagueness on the matter) varies between 31 & 35 USD for non-ASEAN passport holders depending on their country of passport.
There are also some (very minor) charges to be paid for customs (or something

) on the Laos side, but no more than 50 baht each maximum I think.
The bus will also cost you (I believe) 10 to 15 baht each, both ways, depending on the day you go....
You are not charged anything (unless having overstayed

) by Thai Immigration either going or returning...