Hello,
I do a checkup almost every year myself. Before i have done it always at Bumrungrat Hospital. But now i do it at Samitiev, because i have there a free checkup once a year. I can recommend both hospitals. For a normal checkup i need about half a day or even less.
It's actually very easy to do, and at the end you become a report and a short personal talk with a doctor.
What exactly you want to know in details?