@Arlen *****
A tourist visa from the Wellington embassy will get you 60 days. Cost is approx $60. You can extend that once for 30 days and that would get you your three months.
As a NZ citizen you could arrive with no visa and get stamped for 30 days. Also extendable once for 30 days and then do a border bounce to repeat. However your airline may need a onward flight out of Thailand within the initial 30 days allowed with no visa.