Can you extend a 6-month stay in Thailand without exiting the country?

You'll need to show the same documents as when you applied plus residence documents. Is that difficult? Not if you're serious about maintaining an ongoing activity or online work and have the necessary documents ready, just like during the application process. If you're not planning to spend money on a travel abroad, you may just try doing it.

There have been a couple of posts in the group where people have extended in country. One was in Krabi and the other Samut Prakan. Those are the 2 I remember There have been posts about failure but if I remember correctly one was due to finds being below 500k and another with no official proof of the funds. Have a search in the group for more details. Basically you have to show all your original qualification for the visa plus some residential proof add on