You’re right about the embassy/consulate in the first place, but as I said in a previous discussion an onward ticket is according to formal requirements from the Ministry of Foreign Affairs required for both a visa exemption and a tourist visa and therefore the embassy/consulate, airline and the immigration can ask for it. It’s just the Non immigrant visa that formally doesn’t require an onward ticket.
If you hold a Slovakian passport you’ll apply online trough the Thai embassy in Vienna. You can see further information here. I think you’ll be fine with uploading the 87 days ticket as the embassy states that the tourist visa can be extended with additional 30 days.
Yes, I believe OP is from Slovakia. The UK site clearly demands onward ticket for both visa exemption and tourist visa now, but based on feedbacks from UK I know people are approved with an onward ticket after the initially 60 days.
It’s a bit embassy dependent. Some embassies/consulates issues a 60 days tourist visa just with an inbound ticket, most accept an onward ticket within 90 days but some demand 60 days. So unless someone has applied at the same embassy/consulate as you, no one can give you a complete accurate answer. But I suggest you’ll just try to apply with the return flight after 87 days and they will probably notify you by email if they don’t accept this and you might have to change. Ore you just call them and ask first.
These are the general requirements for extension of stay based on marriage in Thailand. There’s no special requirement only for the first year extension and based on feedbacks I know people are denied with the transfer method even though they could show proof of twelve transfers from over sea. I have to leave the discussion here as I only can pass by formal requirements, information from previous discussions and personal feedbacks. If all immigrations would allow transfers for the extension of stay based on marriage it would be great.
“I was told at immigration that the 40k a month had to be income made in Thailand and I couldn't just use my transfers from my UK bank to my Thai bank over the last year.”
Yes that’s my point, “for the following years you can use the monthly transfer method”, and as I said there’s no guarantee that the immigration will accept monthly transfers over sea, unless your embassy offers to give you a affidavit letter. Your particular immigration might accept this, but if you check the formal requirement from the immigration I’ve posted, the transfer method it’s not mentioned as an option and several immigration states that if you don’t have a affidavit letter from your embassy, earn the required 40K baht monthly income in Thailand or bank the 400K baht you don’t qualify for an extension of stay based on marriage.