After reviewing the requirements for the marriage visa on the Siam Legal website, I noticed it states that you must have a visa issued from your home consulate. Is this a requirement? Or is it possible to get one from a surrounding country? What is the difference between a tourist visa or O visa from the States and one from Cambodia?

That is false info.

You can get a single entry non-o visa based upon marriage from any embassy or consulate and then apply for a one year extension of stay (it is not a visa) based upon marriage at an immigration office.

Ive noticed that a proof of address is needed when going to UK embassy to get all your documents. I havent lived in the UK for over 5 years. Been living here in Thailand on Tourist visas. Will the TM30 be ok for my address?

2 minutes ago, Mooner said:

Ive noticed that a proof of address is needed when going to UK embassy to get all your documents. I havent lived in the UK for over 5 years. Been living here in Thailand on Tourist visas. Will the TM30 be ok for my address?

They are not that strict on proof of address. They state this on their website.

Quote

If proof of address is required, we accept driver’s licence, utility bills, postal mail showing your name and local address or house registration.

A rental agreement or a receipt for a room would be accepted also.

3 hours ago, ubonjoe said:

They are not that strict on proof of address. They state this on their website.

A rental agreement or a receipt for a room would be accepted also.

Thanks Ubonjoe!