You give your country you leave from this is primarily for health reaons. If you are coming from a country that requires you to show a yellow fever certificate. Your TDAC will then require you to upload a copy of your vaccination certificate. For flight it is the flight that lands in Thailand. I work a lot in Africa so my first entry after May I went and asked to clarify everything as we used to have to fill out a seperate form. You still have to go to the booth in airport and they check your seat number and give you a slip. Basically if you become ill they can see who you were sitting next to
Getting Pu Yai bans signature also took me the longest was getting him in Amphur building at same time. But had all paperwork already from Marriage and didnt need any extra except copy of latest visa (keep everybit of paper you never know when you need it) Get your pink ID card at same time. Lots of people say its useless, i use it quite a lot just been travelling up north, even got for first time Thai price into national park
oh they do scroll facebook and other social media platforms. Last time met with a friend of a friend who is IO in Krabi he had 4 interns with him and all there job was to go through social media accountd. Your delusional if you think they dont
The solution to your particular problem is to ge married its simple respect of the countres rules and regulations. I had to do same thing 26 years ago in Singapore.
Alternatively take your girlfriend and child to your home country.
These are things you should have thought of before bringing another human into this world.
You want to see Human rights in Thailand go look at some of the refugee enclaves there are a few in Bangkok.