Hi all, I have been living in Thailand for 4 years on a Retirement visa, my Thai wife and I are legaly married, we have 2 children, 5 and 1 who where both born in Thailand, I am now contemplating changing my visa from Retirement to marriage but have a few concerns. My wife is younger than me but what would happen if she were to die before I did, would I have to revert back to a Retirement visa or would I keep the marriage visa because we have children, if so would the visa then finish when the children reached a certain age.Thanks in advance. Any info would be appreciated.

A marriage extension of stay would indeed end with the death of Thai wife. You would be able to obtain support Thai child if legal parent up to age 20 if living with you. You could also return to retirement.

Police order 777/2551 (pinned items useful information or Google) provides all the extension of stay options.

Better to apply for VISA extension to look after your Thai child

Same conditions as marriage extension, take the kid with you to immigration when applying.