NO. if the day for checking is a saturday or sunday, then you come the first weekday. So NO oversty charges. Just look at the immigration pages. And all these people who say that of course you do. They do not know anything about Thai Immigration. Simple.
You will need minimum a NON-O visa, and the workplace normally supply you with the Work Permit. And you will have to have a job, before you can get the Work Permit. But just contact the place you have a job, and then they supply you with the WP. Thats normal.