Thanks for the link, to save anyone else the trouble, it seems that the rate for Bhutan is 89 out of 423 (21%) in country overstays. Average overstay rate for non visa waiver countries is 2.2%.

I don't think it was mentioned, but Bhutan minority groups have experienced ethnic cleansing and oppression; we used to accept their refugees, but now we probably don't, so it's likely that these overstays are actually people fleeing or related to those fleeing persecution. Another fun externality of politicians persecuting immigrants based on statistics.