edsh is right. since it's so easy and such good value to change ur canadian banknotes to baht at bangkok airport as soon as u arrive, there is no reason to change ur money to baht in canada. thai government exchange controls mean that the base exchange rate is about 10% better in thailand compared with in western countries. factor in the fat bank charges and profit margin of most western banks and u're looking at a difference of typically 15%.
the thai exchange counter's profit margin on us dollars can be about 1% less than on canadian dollars but, unless u already have us dollars or can change to us dollars at zero cost, it'll normally be cheaper to bring whatever major western currency u already have in ur hand (loonie included).
ian.