http://www.andamancarrent.com/car.htm
http://phuketindex.com/phuketcarrent/index.htm
http://www.braun-rentacar.com/
My limited driving experience was day time only and had no real problems with my simple suzuki jeep at dusk and night-time a different sort of driving is required as jeep headlights are rubbish and lots of scooters and locals driving around with no lights!!!
so I became a day time explorer only but was worth getting around particularly to nai han and nai yang