Arriving at Bkk Airport without a tourist visa and you will be issued an Exempt Entry Stamp for a 30 day stay.. This is similar to my comment above.. But note: that an Exemption Entry is not Visa but an Exemption to enter without first buying a visa before venturing to Thailand
You have it wrong. Tourist Visas bought at a Thai Consulate before venturing to Thailand are not officially limited - however after several on a year or so you are likely to be pulled out and questioned or denied entry.. Also a Thai Consulate officer who issues Tourist Visas may deny you another or may mark your passport to limit issue in the future
A friend of mine just got her 2nd ED Visa denied because of the inability to pass an informal speaking and understanding Thai Language test at the Immigration office. So I suggest if you are going the ED Visa route for Thai language to stay in Thailand - take it seriously