Thanks for your very helpful message krub. We know who the tenant is. We’ve even sent him a letter (in Thai) under the door a while ago.
Now, we’re thinking of an “extreme” measure (w/ the help of our CCTV) but we need to run it by our directors first.
Also, would you mind if we may attach your note to our (future) correspondence to the family with your name and email address withheld? Please advise.