And if you leave just and enter again just before or on the last day of validity of the visa you still get 60 days of stay and can be extended once with another 30 days which makes it possible to stay almost 9 months.
1. The 1 year Non Immigrant O visa based on marriage with Thai National
2. The Single Entry Non Immigrant O visa based on marriage with Thai National
3. Extension of Stay based on marriage with a Thai National.
Three different things but for easy of the person all named the same.
Name 1 is valid for 1 year and can be obtained from a Thai Embassy or for those legit on-line and gives people a 90 day stay at entry. With border runs it is possible to stay for a period of 15 months.
Name 2 is a Visa that can be used once and give you 90 days of stay, can be bought from a Thai Embassy or can be issued by conversion at Thai Immigration.
Name 3 comes into play for people who already have a Non Immigrant O visa, they can extend their 90 day stay for 60 days based on visiting family or with 1 year based on married to a Thai National.
And as you understand now the 3 different types of short named marriage visa you understand that there are different rules, regulations and laws for each one of them.
As we can not see passports to check your stamps as Immigration Officers love to do, we have to use your given information, best is to use the correct terminology as f.e. I have marriage visa can lead to incorrect advice based on a different option.
Never been an issue for the Royal Thai Immigration Bureau.
But I know, you can find lots of information on line, but most of it seems to be incorrect or given by people who are not informed by the Immigration of Thailand.
Yes, as there is NO restriction in the way to enter Thailand with or without a visa.
Only by land there is the restriction of using 2 Visa Exempt Entries a calendar year.
You might be asked about your purpose of being in Thailand so many times without a proper visa, but that is part of the job from Immigration Officers at check points.