Is a Non-O multiple entry visa valid for 1 year from the first entry into Thailand?

𝗮𝗺 𝗰𝗼𝗿𝗿𝗲𝗰𝘁 𝗶𝗻 𝘁𝗵𝗶𝗻𝗸𝗶𝗻𝗴 𝘁𝗵𝗲 𝘃𝗶𝘀𝗮 𝗶𝘀 𝘃𝗮𝗹𝗶𝗱 𝗳𝗼𝗿 𝟭 𝘆𝗲𝗮𝗿 𝗳𝗿𝗼𝗺 𝗳𝗶𝗿𝘀𝘁 𝗲𝗻𝘁𝗿𝘆

Nope you are sadly NOT correct. 😮 A year-long, multi-entry Non-O visa is valid for a year from the date it's ISSUED by the Thai embassy/consulate not the date you enter the country on 😕

Look on the visa itself, it will have a date of issue and a 'valid until' or 'must enter by' date.

A year/multi Non-O visa gives you ulimited entries of 90 days each for the validity of the visa itself. If you were to exit/re-enter the country just before the VISA (not your current entry stamp) expired you'd get another 90 day entry stamp