As
@Tod ********
replied earlier...
okay, you have 3 extension options available to you...
1 - a year extension based on raising a half thai child (if the child was born out of wedlock you need to have been granted legal parental rights thru family court or the local Amphur) you also need 400K baht in a thai bank account in your name only...
2 - a 60 day visit thai family extension based on having a half thai child (this doesn't require proof of legal parental rights or any financial requirements)..
BUT YOU SAID YOU ALREADY HAVE USED THIS FAMILY VISIT EXTENSION...
3 - a 60 day unable to travel due to covid 19 extension...
ALL extensions inside the country are 1900baht no matter the length of time they're issued for.
Go to your immigration office and ask what the requirements are for the extension you're wanting to get.
I will add one more...
Get Married