[DownloadMan]

if you have a work permit and as far as I know, you do need one if you are employed by your own co.Maybe he had a multi-entry of some kind.
But if you have an "O" visa, either married or retirement then it is not necessary to leave the country to renew it, just go to an immig. office and get it done in a short while, less than an hour usually.
But I have found that you do not really want to put a lot of stock in what some farang tell you as sometimes they just like to talk about what they know and not always tell it like it is..But you can not put much stock in the published immig. laws either as they never are as printed when you go to get the visa either, each officer can and does make some up as they go along.
If you have everything done that is in the laws you read, then you are pretty safe, but do not be surprised if there is something you have to do that is not mentioned.