I could never quite figure it out. They give me a one-year visa, and then tell me to come back every 90 days to confirm I am still here. One of the mysteries of the Land of Smiles, I guess. But my 4th 90-day slip runs out about a week ahead of my year-long visa. Last year the secretary phoned the visa office and asked if it would be ok to let it ride for the extra week until I came to do the visa, and they said fine, and no problems later. This year we did the same thing. And then when we showed up for the new visa, and gave them the 90-day renewal form, they got all huffy about the law is the law - and nailed me for 2000 baht because it was about a week late. I've also been tagged 600 baht per for my last couple of Amazon parcels - maybe there's a new 'steal from the farangs at every opportunity' drive going on - just a heads up to be sure to dot your i's and like that if you're thinking of letting a 90-dayer go for a few days.