Best is to open your own company if you want some extra income. But for this you’ll need to hire Thai employees. Usually costs about 20k THB to open a company. The line between owning a company and working is a bit grey, but as long as you’re not doing active work it should be fine.
Sometimes i think its easier to just pay it. Even if you have all the requirements as listed officially, they can ask for this and that extra and you end up wasting a lot more time at immigration. Not worth it for me.
I’m guessing this post is why the admins of the original Thailand Visa Advice group are so strict about it. So much misinformation and rubbish comments here.
For most cases, you can extend 30 days at the immigration office so I’m guessing that will apply to you too. If you want more detailed advice, then you will have to give more detailed info.