If you have an extension of stay based on retirement using the THB800,000 in the bank method, ie you're not old enough to collet a pension, and you get an offer of employment with a work permit, do you have to change to a non-immigrant B visa outside Thailand or can the retirement "visa" be used to apply for a work permit?

It's a hypothetical question at this time but I am interested to know.

A work permit is not issued on an extension of stay based on retriement.

You will have to get a non-B visa, athough it might be possible to change your reason of stay from retirement to employement. But that will depent on your immigration office.

Get old fast.. over 55 than apply for the retirement visa.. That is what I did.. I lived many years in europe and then about 25 extra years in the USA after that.. got here ay 56 and it was a breeze after that.. Make you money first then think about Thailand.. Thailand has been here a long time.. It will be here after you get old enough.. to be a senior citizen.. So,l go enjoy the west until you are old enough to retire.

Just went through this. Had a retirement visa with sever extensions of stay since 2005. Had to leave the country, give up my retirement extension of stay, get a non immigrant B and then apply for a work permit.

Actually retirement extension of stay or long stay visa is available to anyone older than 50 who meet the qualifications.