How can I obtain a 60-day Thai tourist visa while in Thailand?

So then you have answered your own question. You say that the process may be complicated and you don't want to book a flight tickets......and that is directly due to the consulate that you have chosen. if you want it to be easy with no need for onward tickets or anything else then go to Vientiane. If you want to go to another consulate, then be prepared to have all the required paperwork ;) Eventually you will have problems with the 30 tourist visa exemption process as they do not allow people to stay long term in Thailand as you you are not a tourist. Good luck.

Be aware that for a lot of countries there is a limit of two land border crossings a calendar year using the Visa Exempt Entry stamp. With or without a visa you have to leave at the end of you Admitted until date or apply for an Extension of Stay, so it seems easy enough for me to count from the day I enter Thailand 88 days onward and buy a ticket on that day to leave Thailand. It is not rocket science.

This is what they say: Evidence of travel from Thailand (air ticket paid in full). At this Embassy you need to show you leave Thailand after the maximum 90 days.