the process is as you went through, they will stamp you first for 30 days and next time stamp you again for another 30, without having to do all the paperwork. (although I didn't know that, and the 2nd time I went I still was told to fill it out, but then I didnt have to give it to anybody).
Your visa should be okay definitely until 9th June and I'd say you're likely to also get the 2nd stamp for the extra 30 days. But of course I can't really speak for the actual immigration office.
30k thb? not worth it. A UK tourist visa application is pretty straight forward. All agents do is collect your personal information, which you have to provide anyway.