What should I do if my Thai visa's date of validity is incorrect?

Most visas for countries have a validity starting with the date they are issued and expire either at the end of that period or when you enter the issuing country. The period of stay is a different thing depending again on the issuing country and the type of visa you have

Visas always start at the approval date.

My Non-O from Los Angeles was 90 days from date of issue. Took exactly 2 weeks to process. They said it could take up to 3 weeks to process. But the date they issue it is the date your visa starts regardless of your actual date of entry. Just the way it is. Make sure they stamp you correctly on arrival! I had to get my stamp changed to open my bank account. IO at airport was looking at my Visa but stamped me in as 60 day exempt. I did not check, but luckily the bank told me how to have it changed and that worked. Live and learn, and just keep smiling to the Officers, it really does help!

90 days to enter and once entered Thailand 90 days validity of the visa.

All visas run from the date of issue

Matthew Wheeler . . . . The website of the Royal Thai General Consulate Frankfurt says clearly:

“Don’t apply for a visa earlier than 3 months before your planned trip”

Usually, many people, including you, are confusing the visa validity with the duration of the stay permit you will receive upon entering Thailand based on a visa

You visa is VALID for use for an entry, for 90 days, beginning on the date of its issue

If you enter Thailand within this validity period, you will be stamped in for a 90-days stay permit. Or for a 60-days stay permit if you have a tourist visa. The visa itself will EXPIRE and become invalid when you enter, if it is a single entry visa. Only multi entry visa will remain valid for the full length of their validity

Il ne faut pas de visa pour voyager en tant que touriste vous avez 60 jours d'office avec moyen de rallonger de 30 jours sur place.

The approval of the visa gives you 90 days to enter the country within that 90 day period.

Your visa is correct. It runs from the date of issue. Depending on the visa you applied for that would normally be 90 days from issue.

If you’ve applied too early then that’s on you. You’ll rarely have any luck contacting an embassy but even if you could it wouldn’t change the fact that your visa is correct.

I would think you have 90 days to enter Thailand from date of approval, that's normally the case. I think you are fine...