@Martha ***
I'm a Software Developer working remotely on contract.
I am not aware of any requirement to enter Thailand within a certain time period.
The visa just says 'valid from' and 'valid until' a date 5 years later.
They didn't provide any additional information to me when I picked up my passport.
Just handed me my passport, smiled and moved on to the next person.
If it's anything like the METV which I have had before, there is no entry requirement timeframe, and your stay duration will be determined by the entry stamp you get at immigration. I expect I will get a 6 month stamp next time I enter Thailand. Which I should be able to extend later at the Immigration office.