Anonymous ******************
@Ben *******
That’s flat out incorrect. The visa is active from the moment it is issued and the only difference between entering a day or a year after it is issued is that you have less time left on the visa.
People are conflating consular offices not processing applications where the anticipated date of arrival is more than 3 months out and this “activation period” which doesn’t exist for multiple entry visas.
Single entry visas like a Non-Immigrant B/O/ED are normally only valid for 90 days so you do need to enter Thailand within 3 months or the visa expires but multiple entry visas are active from the date of issue.