There may be multiple codes to access an international network. IIRC, 011 (or was it 0288?) once was the U.S. code to call overseas via AT&T but other carriers could be selected via different prefixes. In Thailand prefixing 009 for international call may be cheaper than a 008 prefix, and either is cheaper than ‘+’ which, I think, defaults to the non-discounted plan of your main carrier.
There are even in-country prefixes. Calling Bangkok from upcountry Thailand via pay phone was ridiculously expensive in the 1990’s (far more expensive than calling U.S.A.) unless you knew to first punch a 1234 prefix. (I think the prefix was 1234; I’ve not used a pay-phone here for decades.)