DTV is Destination Thailand Visa and you may qualify depending if you are studying in one of the approved study areas that qualify for a DTV.
Other than that if you don't qualify then perhaps a 6 months multiple entry tourist visa would suit you which can be stretched out to 9 months depending on your exits and entries..
If you are planning on being in Thailand on a long term basis then either of those are safer options than trying to rely on Tourist exemption entries..
Both the DTV and 6 month multiple entry tourist visa need to be arranged outside of Thailand before you travel.