Can Brazilian expats extend their visa by making a run to Myanmar from Chiang Mai?

Just to summarize: It seems you can get 90 days Visa Exempt Entry by bi-lateral agreement at Laos border, out of earlier reports not at the Cambodian border and nobody knows about Mea Sai or Mae Sot to Myanmar. There is enough information from the Ministry of Foreign Affairs posted, but unfortunately they are not in charge of the Immigration Checkpoint. It also seems to be mentioned in a Vienna Convention, but if that all is going to help when an Immigration Officer says no, I doubt it. If you like to find out, your closest border Mae Sai will let you make a new run for this 90 day Exempt Stamp it will be a try out. If you decide to do this please report back with your experience. In the mean time, I guess all options are discussed.

Even though there is a bi-lateral agreement between thailand and the 5 countries (Argentina, Brazil, Chile, Peru & South Korea) so that they get 90 days when they enter thailand different land borders will NOT let people from those countries bounce out and back in to get another 90 day visa exempt entry.

I am not sure people from those countries can bounce out and back in at the Myanmar border crossings at Mae Sai or Mae Sot...

People from FIVE countries (Argentina, Brazil, Chile, Peru and South Korea) get a 90 day visa exempt entry when they come into thailand. Out of reports you only can do this when you fly out and back in.