How can a French citizen obtain a 2-3 month Tourist visa while in Thailand?

you do know that you can get a 30 day extension on the 30 day visa exempt entry you have now at the immigration office for 1900baht right?

Any of the thai consulates in the area are going to be fine for you to use for a single entry tourist visa. Just so you're clear when you get the visa it's valid for 90 days <- that means you have 90 days to ENTER thailand and you will get stamped in for 60 days when you do. You can get a 30 day extension on top of that from the immigration office for 1900baht.

When I say any thai consulate will work I mean as long as you meet the requirements listed on their website. Currently the thai consulate in Vientiane Lao does NOT require proof of funds, proof of onward travel or proof of a hotel booking <- SO if you have any problems meeting those requirements Vientiane is the consulate you want to use.

All the other consulates in nearby countries require some or all of those 3-proof-ofz; proof of 20K baht in a bank account, proof of onward travel within 60-90 days, and proof of a hotel booking. Check the website of the consulate you are going to go to so you can be prepared for what they require.

Good luck

Yes, I did it in Kuala Lumpur (the advantage is that you do not need a visa for Malaysia). On the website they provide you the list of the docs you need to show off. You give your papers in the morning and get your visa the next afternoon 👍

Go to Vientiane and apply for single entry tourist visa (60 days)...1000 baht. You can extend this visa at any immigration office in Thailand an additional 30 days for 1900 baht.