you are receiving a lot of unrelated info here, as most people are not common with the special laws and regulations in Germany regarding residency, proofs of address, bank accounts et cetera. Mainly Dany Nomads' advice is completely useless as he is not aware that you canot fulfill the requirements asked on the Berlin embassy website, no matter how you turn or twist it
applying in Vietnam or Vientiane/Laos is the easier option, as you can prove by the stamp in your passport that you have entered their country. However in Vientiane, AFAIK the embassy requires a proof that you had a minimum of 500,000 THB in your account for the last three months
a foreigner first needs a Non-Imm-B visa, in order to apply for a work permit. So, in order to change the visa or receive a Non-Imm-B visa, a foreigners needs to invalidate his existing visa or stay permit, which in most cases is done by exiting Thailand without a re-entry permit
I'd say it is not such a good answer, most of all the last sentence doesn't make any sense . . . . . . .as you can't work on ANY of the visas Ralph listed - you won't even get a work permit issued
at some point, after they have checked your passport stamp history, even the "visa run agencies" will refuse to take you to the border. They know at which point your chances are exhausted
your whole entry history is saved on Immigration's Central Computer. You will get "flagged" once you get pulled aside and asked about your intentions to stay in Thailand. Once flagged, every border official will see that you have already been warned to get the proper visa for your purpose of stay. So, if they warned you once, there is no visa-exempt entry for you awaiting the next time you try your luck
then have her phone number ready on your mobile phone, so she can explain it to the Immigration officer. Or like Graham recommends, have an invitation letter to show