Im travelling outside thailand and want to return to thailand a few months from now.

If I get my tourist visa today how long will it be valid for untill I use it?

Im travelling outside thailand and want to return to thailand a few months from now.

If I get my tourist visa today how long will it be valid for untill I use it?

3 months validity from the date of issue. So might you might be better off to get one only when you are ready to return to thailand. Say a week before your arrival in the kingdom.

As said 3 months from issue but there is no reason to wait if you know you will be returning prior to the end of the three month validity. You get the same sixty day entry plus option to extend 30 days with an entry on day one or day 89.