In GPS - Maps tells the stories.

For Thailand itself there is so many software and maps.
I tried almost all of them. Powermap, Papago, Garmin, Miomaps, Sygic, Ndrive. TomTom, Navitel & others.
Which is the best I can't tell exactly. Only difference is maps colours and some features pending on the software and device.

Most important - find a device and software that has map availability and continue support.
No specific brand - as long as it is reliable and accurate.