https://play.google.com/store/search...nd+maps&c=apps
http://www.thaivisa.com/forum/topic/...-which-better/
http://www.thaivisa.com/forum/topic/...-thailand-map/
Mobile data is relatively inexpensive here, Google Maps works fine on 2G. Streetview is handy, as is Google Maps Directions which incorporates public transportation.
Google Maps caching (of off-line map squares) and Google Turn-by-turn Navigation works but requires hacking.
If you have a Garmin nuvi GPS system it is pretty easy to find and load a map for Thailand.