the best way is by SWIFT transfer to your Thai bank account. This will give you the needed FET, foreign exchange transaction, receipt needed if you change your mind in the future and want to transfer the lump sum out of Thailand, especially with the investor visa through the BOI.
inside Thailand you can not get the type O visa extension without having bt400,000 in your Thai bank account first, and you can not get a Thai bank account on any tourist entry. How are you going to get your Thai bank account in order to get your type O visa extension after you are married? You must have the type O visa extension in order to get your bank account. You can not get one with just your marriage documents, and on a tourist entry.
Be fully aware that in Bangkok when applying for the residency certificate they mail it to you to make sure the address you listed is accurate, and it takes a week to ten days to receive.
the big difference is that on the type O extension based on Thai wife, you can get a work permit to work in Thailand. You can't do that on a DTV. Also, being married to a Thai, and working in Thailand, and paying your taxes for three years, plus other documents, etc, you have a route to apply for Thai citizenship after just three years, or get permanent residency, something you can't do on the DTV. A type O based on marriage has it's advantages.
the 7 days to leave by stamps are given to people who's visa, or extension, is expiring, like lots of business people getting laid off with no warning, or tourists that can't get another extension, but try to apply for one anyway (and is used the most), when their entry is about to expire, not when they intentionally cancel their entry stamp.