For tourists who have visa exemption, Do they have to fill any online form or paper for immigration inward formality?

Due to my bf will come to visit me. It's his first time in Thailand. I just want to make sure that everything going smoothly.

Hey, I have a peruvian passport and, so I get an exemption visa for 90 days. I've thought I was able to get an extension for another 90 days or at least 30 days more, but today I went to the immigration office and they told me they could only give me another 7 days. I'm not even sure, because the officer didn't speak english very well. Does any of you have been on a similar situation?

I've also thought of going to Cambodia for one week and come back, do you guys think that might be risky? I don't want to go there with a big suitcase, but I'm not sure if they will let me come back to Thailand with no problem 🤔

Just to mention is my first time in Thailand, and my passport has many stamps from other countries within the last year.