http://www.bumrungrad.com/ is the place I use. It's a bit more than $200 for MR, etc., but I'm doing the exec screening w/ stress test and ultrasound (http://www.bumrungrad.com/en/health-check-up-bangkok-thailan...) and x-ray, and may do MR and would potentially get a CT (obviously avoid CT if you don't need it due to the radiation dose, but with modern equipment I'm personally not super worried).

I got my LASIK done about 8y ago at TRSC (www.lasikthai.com) which means free checkups and touchups for life, too, also down the street. Eye exams are one case where I usually use a hotel car vs. a taxi to get around, as dealing with obnoxious taxi drivers while sort of blind sucks.