Hello there. When you come into the kingdom, they give you a 30 day stamp, which you can then extend for another 30 days at immigration if you pay 1900. How many times can you extend it? Are you allowed to do it once only? What then? Have to leave the country?

One 30 day extension per entry.

After that you would need to exit Thailand and reenter if you wish to stay longer.

That exit and reentry can be a simple border bounce for a visa exempt entry. 

Will give you 45 day stamp from Oct 1.

okay thanks