Best bet is for him to turn off Data Roaming so as not to incur charges, which could be astronomical. Wifi is generally available in Thailand, so he will be able to send and receive messages free while on wifi.
Yes you can use iMessage. My friend lives in Scotland and that's how we text. I love it!! Just make sure you turn of "send message as text if iMessage is unavailable" because then it'll send as a text if they aren't available
Via iMessage. Them you'll pay for them.
~ iPhoneMommy ~
"Be nice to those you meet on the way up because you will meet them on the way down."
What happens if the recipient is not in a wi-fi area?
Does it hold the message and deliver it later? It seems to do that if I put one phone in Airplane Mode.
Is there a limit to how long it will hold it?