@Rossano **************
if your plan consists of entering again on a 30 days visa-exempt entry, then this would be you second consecutive visa-exempt entry.
You could be grilled by Immigration upon entry, for the actual purpose of your visits.
So you better be prepared to show, have the three proofs:
**** proof of 20.000.- THB in CASH. Can be in another currency, though
**** proof of accommodation of the next 3-4 nights in Thailand
**** proof of onward travel OUT of Thailand within the 30 days you will get stamped in