I read lot of good advice for you in the comments.
So you are new to Thailand and probably don't speak or understand Thai language yet.
Do yourself a favor and go to a school to learn Thai language first. Because, you will learn so much about Thailand, the Thai people and your gf. At which time you will be confident if and who you want to marry in Thailand.
Finally, i recommend to you visit Bang Kapı, which is about 45 min by boat from the city center. You might like it there.
I did it at the embassy in PP and took 2 days back then.
The first time I went there to ask them for info, the only response they had for me was "check the website". So it wouldn't surprise me if they don't reply to email or answer phone.
If you mean Visa from the Thai embassy in Cambodia, I've gotten a TR VİSA from them in 2021. I will be glad to help as much as I can. What are your concerns?