If you have trouble finding a doctor to do the medical certificate (the requirements are quite specific), look specifically for a travel medical clinic. They are prepared to do the test for elephantiasis, for example, whereas a GP likely would not.

@T**

has described exactly the process we used when we came to the Kingdom from the US in November 2015. Pay close attention to the second part: while the retiree will be stamped in for a year, the piggybacking spouse will be stamped in for 90 days only!

Jeff Jue Xjs - I was in your exact situation with my multi-entry O-A visa, and as my "enter before" date approached, based on Tod's advice, I did a day trip to exit / reenter to get stamped in for the additional year. I chose to fly to Kuala Lumpur in the morning and back to BKK that night just for the stamp. Cheap flight, no visa necessary to enter Malaysia, and it worked perfectly.