Well. If you buy the device in Thailand it may include the map in the price. In this case it would be relatively cheap. Then, if you buy your unit somewhere abroad you will have to pay 4.500,- Baht (about USD 128) for the map.?
Sometimes it may be a bit complicated, especially when your GPS receiver has less then 100 MB memory. For these receivers ESRI does not provide a map on a CD. You will have to go directly to their office or ask help from your dealer.