Yes. Tourists did not visit Thailand anymore. Beaches were empty. Restaurants were empty. They still did not recover from the economic damage because there were no tourists spending money years ago.
If your name is on he Thai birth certificate you can get a 3 month Non O visa at the Thai consulate for taking care of your child. You can extend that visa with 2 months if you take your girlfriend + child when applying for he extension. That is what I always do. In the case 5 months is not enough you can go to Laos and quickly back for a 1 month VE. Which can also be extended with1 month. I did that once when my 5 months were not enough. If you want a Non O for more than 3 months you need to officially recognize your child in Thailand.
Check in online and not at the check-in counters in the airport. The chance that they are going to look at your carry on bag is very small when there is a long line for boarding.