This is a very late reply, but I must have missed this earlier and someone just dug it up. Sprint uses CDMA, there is no SIM for any CDMA phone out there, unless you want to pay a ridiculous sum for that tri-band phone. The only two technology's I know of that use SIM's are GSM and AT&T/Cingular which I think is GSM as well. Nextel also use's SIMs however I think all networks I've seen in Thailand use GSM. I don't think you can even roam with a Sprint (Hawaii or wherever) phone. I already tried a few trips ago.
