How long can I wait to use my approved visa for Thailand?

You can use it by entering Thailand until the last date of the visas validity.

???? Date on Visa, Just Saying

As Brandon says most are valid for 90 days. No issue applying early for one of those to “check it off the list”. As long as you enter by the valid until date you’d be stamped in for the number of days that visa allows.

However you wouldn’t want to apply too early for something like the METV (valid for 6 months) or OA (valid for one year) because you’d be wasting days from the time it’s issued. Timing border bounces right with those two visas you can get nearly 9 months or two years respectively.

Most visas are valid for 90 days from the day it is issued. There will be a date on the visa that you must use it by.