What are the limitations and rules for staying in Thailand on a tourist visa?

First off there is NO such thing as a 30 day tourist visa :/ If you showed up here without having bought a visa from a thai consulate before hand and you were stamped in for free it would be on a 30 day visa exempt entry stamp.

Be that as it may,.

There is no way to extend a 30 day visa exempt entry or a 60 day tourist visa entry for 30 days more than once per entry.

I'd say your best bet would be to go back to your country and get a 6 month METV <- which would give you almost 9 months of stay (in 60 day increments).

You're playing a dice game with a country that has been advancing a systematic program for 3 years straight to limit and deny back to back stays using Exemption Entries and Tourist Visas to basically live in Thailand. Are you not aware Thailand does not want you to stay in Thailand using the methods you are trying to use? ... At a pace of about every 3 to 6 months the limits are purposely tightened. My prediction ...In about about another 9 months to one year - under age 50 people staying in Thailand for more than 60 days a year on SETV and Exemption Entries will come to halt. My Opinion... based on close observation over about a continuous 5 years.

On the BKK airports and the Malaysian Border they want to se 20.000 Thb or equivelant currency in CASH. The can also ask for proof of accommodation and onward travel, the bigger your history of staying in Thailand using Visa Exempt Entry and Tourist visa is the more chance to get questioned. Be prepared.

Be prepared to show an onward ticket and 10k baht.

There is no limit on tourist visas or air entries, nor any limit of any kind on time in Thailand. That said, you can expect hassles and questioning eventually from immigration.

There is no 180 day in any year rule any more. HOWEVER, as this will be your 6th visa exempt entry, expect to be flagged for questioning about how you support yourself here.

Why not get a tourist visa from a Thai Consulate or Embassy in your home country ? Questioning by Thai Immigration at the airport about your repeated entries may occur. With or without a Thai visa. See recent postings from those questioned.